Research Library


Health Effects of Substance Use

Trajectory of adolescent cannabis use on addiction vulnerability

The adolescent brain is a period of dynamic development making it vulnerable to environmental factors such as drug exposure. Of the illicit drugs, cannabis is most used by teenagers since it is perceived by many to be of little harm. This perception has led to a growing number of states approving its legalization and increased accessibility. Most of the debates and ensuing policies regarding cannabis were done without consideration of its impact on one of the most vulnerable population, namely teens, or without consideration of scientific data. We provide an overview of the endocannabinoid system in relation to adolescent cannabis exposure and provide insights regarding factors such as genetics and behavioral traits that confer risk for subsequent addiction. While it is clear that more systematic scientific studies are needed to understand the long-term impact of adolescent cannabis exposure on brain and behavior, the current evidence suggests that it has a far-reaching influence on adult addictive behaviors particularly for certain subsets of vulnerable individuals.

Hurd, Y. L., Michaelides, M., Miller, M. L., & Jutras-Aswad, D. (2014). Trajectory of adolescent cannabis use on addiction vulnerabilityNeuropharmacology, 76, 416-424.


How Drugs Effect the Brain 

Diane Rehm Speaks with Dr. Nora Volkow, Director of the National Institute on Drug Abuse.


Substance Abuse Treatment for Persons With Co-Occurring Disorders

This guide gives substance use disorder treatment providers information on mental illness, substance use disorders, or both. It discusses terminology, assessment, and treatment strategies and models.

Center for Substance Abuse Treatment. (2005) Substance Abuse Treatment for Persons With Co-Occurring Disorders. Treatment Improvement Protocol (TIP) Series 42. DHHS
Publication No. (SMA) 05-3992.


Comorbidity: Addiction and other Mental Illnesses

Comorbidity is a topic that our stakeholders––patients, family members, health care professionals, and others–– frequently ask about. It is also a topic about which we have insufficient information, so it remains a research priority for NIDA. This Research Report provides information on the state of the science in this area. Although a variety of diseases commonly co-occur with drug abuse and addiction (e.g., HIV, hepatitis C, cancer, cardiovascular disease), this report focuses only on the comorbidity of drug use disorders and other mental illnesses.

To help explain this comorbidity, we need to first recognize that drug addiction is a mental illness. It is a complex brain disease characterized by compulsive, at times uncontrollable drug craving, seeking, and use despite devastating consequences— behaviors that stem from drug-induced changes in brain structure and function. These changes occur in some of the same brain areas that are disrupted in other mental disorders, such as depression, anxiety, or schizophrenia. It is therefore not surprising that population surveys show a high rate of co-occurrence, or comorbidity, between drug addiction and other mental illnesses. While we cannot always prove a connection or causality, we do know that certain mental disorders are established risk factors for subsequent drug abuse— and vice versa.

It is often difficult to disentangle the overlapping symptoms of drug addiction and other mental illnesses, making diagnosis and treatment complex. Correct diagnosis is critical to ensuring appropriate and effective treatment. Ignorance of or failure to treat a comorbid disorder can jeopardize a patient’s chance of recovery. We hope that our enhanced understanding of the common genetic, environmental, and neural bases of these disorders—and the dissemination of this information—will lead to improved treatments for comorbidity and will diminish the social stigma that makes patients reluctant to seek the treatment they need.

National Institute on Drug Abuse. (2010). Comorbidity: Addiction and Other Mental Illnesses. Rockville, MD: NIDA.


Addiction and Cognition

The brain regions and neural processes that underlie addiction overlap extensively with those that support cognitive functions, including learning, memory, and reasoning. Drug activity in these regions and processes during early stages of abuse foster strong maladaptive associations between drug use and environmental stimuli that may underlie future cravings and drug-seeking behaviors. With continued drug use, cognitive deficits ensue that exacerbate the difficulty of establishing sustained abstinence. The developing brain is particularly susceptible to the effects of drugs of abuse; prenatal, childhood, and adolescent exposures produce long-lasting changes in cognition. Patients with mental illness are at high risk for substance abuse, and the adverse impact on cognition may be particularly deleterious in combination with cognitive problems related to their mental disorders.

Drug addiction manifests clinically as compulsive drug seeking, drug use, and cravings that can persist and recur even after extended periods of abstinence. From a psychological and neurological perspective, addiction is a disorder of altered cognition. The brain regions and processes that underlie addiction overlap extensively with those that are involved in essential cognitive functions, including learning, memory, attention, reasoning, and impulse control. Drugs alter normal brain structure and function in these regions, producing cognitive shifts that promote continued drug use through maladaptive learning and hinder the acquisition of adaptive behaviors that support abstinence.

In a 2005 review, Steven Hyman stated the current neurological conception of drug abuse concisely: Characterizing addiction as a disease of “pathological learning,” he wrote, “[A]ddiction represents a pathological usurpation of the neural mechanisms of learning and memory that under normal circumstances serve to shape survival behaviors related to the pursuit of rewards and the cues that predict them.”

This article reviews current knowledge on the cognitive effects of drugs and their neurological underpinnings. These effects may be particularly disruptive when individuals are exposed to drugs during brain development, which lasts from the prenatal period through adolescence, and in individuals with mental disorders. An understanding of these issues will help substance abuse clinicians identify and respond to cognitive changes that affect patients’ responses to treatment.

Gould, T. J. (2010). Addiction and cognitionAddiction Science & Clinical Practice5(2), 4–14.


Substance Abuse and Brain Development

Adolescence is a unique period in neurodevelopment. Alcohol and marijuana use are common. Recent research has indicated that adolescent substance users show abnormalities on measures of brain functioning, which is linked to changes in neurocognition over time. Abnormalities have been seen in brain structure volume, white matter quality, and activation to cognitive tasks, even in youth with as little as 1–2 years of heavy drinking and consumption levels of 20 drinks per month, especially if >4–5 drinks are consumed on a single occasion. Heavy marijuana users show some subtle anomalies too, but generally not the same degree of divergence from demographically similar non-using adolescents. This article reviews the extant literature on neurocognition, brain structure, and brain function in adolescent substance users with an emphasis on the most commonly used substances, and in the context of ongoing neuromaturational processes. Methodological and treatment implications are provided.

Squeglia, L. M., Jacobus, J., & Tapert, S. F. (2009). The influence of substance use on adolescent brain developmentClinical EEG and Neuroscience : Official Journal of the EEG and Clinical Neuroscience Society (ENCS)40(1), 31–38.


Persistent cannabis users show neuropsychological decline from childhood to midlife

Recent reports show that fewer adolescents believe that regular cannabis use is harmful to health. Concomitantly, adolescents are initiating cannabis use at younger ages, and more adolescents are using cannabis on a daily basis. The purpose of the present study was to test the association between persistent cannabis use and neuropsychological decline and determine whether decline is concentrated among adolescent-onset cannabis users. Participants were members of the Dunedin Study, a prospective study of a birth cohort of 1,037 individuals followed from birth (1972/1973) to age 38 y. Cannabis use was ascertained in interviews at ages 18, 21, 26, 32, and 38 y. Neuropsychological testing was conducted at age 13 y, before initiation of cannabis use, and again at age 38 y, after a pattern of persistent cannabis use had developed. Persistent cannabis use was associated with neuropsychological decline broadly across domains of functioning, even after controlling for years of education. Informants also reported noticing more cognitive problems for persistent cannabis users. Impairment was concentrated among adolescent-onset cannabis users, with more persistent use associated with greater decline. Further, cessation of cannabis use did not fully restore neuropsychological functioning among adolescent-onset cannabis users. Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.

Meier, M.H., Caspi, A., Ambler, A., Harrington, H., Houts, R., Keefe, R., McDonald, K., Ward, A., Poulton, R., and Moffitt, T. (2012) Persistent cannabis users show neuropsychological decline from childhood to midlife. PNAS. 109(40), E2657–E2664.


Teen Drug Use and Addiction

Initial and experimental stages of tobacco and alcohol use during late childhood: Relation to peer, parent, and personal risk factors

A staged model of smoking adoption has been widely applied in studies of adolescent smoking. The present study applied this model to examine the preliminary stages of tobacco and alcohol use by children. Using discriminant analysis, factors associated with the abstinence, initiation, and experimentation stages of tobacco and alcohol use were compared in a sample of 1,272 children in grades 4 and 6. Modeling of use by best friends and the perceived prevalence of use among same-age peers were most strongly related to the initiation and experimentation stages of tobacco and alcohol use. Other key factors were offers from parents and friends, adjustment to school, and behavioral self-regulation. The weakest factors were parental modeling and self-esteem. The initiation and experimentation stages are not as highly differentiated among children as other studies have found them to be among adolescents, suggesting that if initiation occurs during childhood, progression to experimentation is likely. Prevention programs could simultaneously influence children's risk of tobacco and alcohol use by targeting the common risk factors for preliminary use of these substances.

Jackson, C. (1997). Initial and experimental stages of tobacco and alcohol use during late childhood: relation to peer, parent, and personal risk factorsAddictive Behaviors22(5), 685-698.


Patterns of drug use from adolescence to young adulthood: III. Predictors of progression

Possible linkages of influence among classes of drugs in the observed sequential progression from adolescence to young adulthood are investigated through event history analyses. Three stages are examined: initiation to marijuana, to the use of other illicit drugs, and to prescribed psychoactive drugs. The data are based on a follow-up cohort of former adolescents representative of high school students in grade 10 and 11 in New York State who were reinterviewed nine years later at ages 24-25. The sequential order between alcohol and/or cigarettes and marijuana reflects not only the effect of the use of legal drugs on marijuana initiation, but also age effects on onset of these drugs, controlling for individual characteristics measured in adolescence; marijuana use by one's friends in adolescence is an additional important predictor of marijuana initiation. Prior use of marijuana is necessary for progression to other illicit drugs. Multiple factors are involved in the progression to prescribed drugs, with adolescent depressive symptomatology and use of other illicit drugs important for both sexes, and maternal use of psychoactive drugs, dropping out of school, and prior use of marijuana of additional importance for women. Although licit drugs influence initiation into marijuana independently of age effects, it is especially for the progression from marijuana to other illicit drugs that the earlier drug is associated with the progression to a higher stage drug.

Yamaguchi, K., & Kandel, D.B. (1984). Patterns of drug use from adolescence to young adulthood: III. Predictors of progressionAmerican Journal of Public Health, 74(7), 673-681.


Evaluating the drug use “gateway” theory using cross-national data: Consistency and associations of the order of initiation of drug use among participants in the WHO World Mental Health Surveys

Background: It is unclear whether the normative sequence of drug use initiation, beginning with tobacco and alcohol, progressing to cannabis and then other illicit drugs, is due to causal effects of specific earlier drug use promoting progression, or to influences of other variables such as drug availability and attitudes. One way to investigate this is to see whether risk of later drug use in the sequence, conditional on use of drugs earlier in the sequence, changes according to time-space variation in use prevalence. We compared patterns and order of initiation of alcohol, tobacco, cannabis, and other illicit drug use across 17 countries with a wide range of drug use prevalence.

Method: Analyses used data from World Health Organization (WHO) World Mental Health (WMH) Surveys, a series of parallel community epidemiological surveys using the same instruments and field procedures carried out in 17 countries throughout the world.

Results: Initiation of “gateway” substances (i.e. alcohol, tobacco and cannabis) was differentially associated with subsequent onset of other illicit drug use based on background prevalence of gateway substance use. Cross-country differences in substance use prevalence also corresponded to differences in the likelihood of individuals reporting a non-normative sequence of substance initiation.

Conclusion: These results suggest the “gateway” pattern at least partially reflects unmeasured common causes rather than causal effects of specific drugs on subsequent use of others. This implies that successful efforts to prevent use of specific “gateway” drugs may not in themselves lead to major reductions in the use of later drugs.

Degenhardt, L., Dierker, L., Chiu, W., Medina-Mora, M., Neumark, Y., & Sampson, N. et al. (2010). Evaluating the drug use “gateway” theory using cross-national data: Consistency and associations of the order of initiation of drug use among participants in the WHO World Mental Health SurveysDrug And Alcohol Dependence108(1-2), 84-97. 


 

A Molecular Basis for Nicotine as a Gateway Drug

On the historic occasion of the 122nd Shattuck Lecture and the 200th anniversary of the New England Journal of Medicine, we chose to address a topic that is at once scientific and personally historic. In recent debates over legalizing marijuana, from all-out acceptance in Colorado to narrow decriminalization in Maryland, the scientific question of the role of marijuana as a gateway drug (i.e., a drug that lowers the threshold for addiction to other agents) has loomed large. Both opponents and proponents of legalization have distorted what science does and does not tell us — and both sides have overlooked the importance of nicotine as a gateway drug.

Epidemiologic studies have shown that nicotine use is a gateway to the use of marijuana and cocaine in human populations. What has not been clear is how nicotine accomplishes this. In this article, we describe how our personal collaboration allowed us to bring the techniques of molecular biology to bear on this question and to reveal the action of nicotine in the brain of mice. We then apply our conclusions to the public health concerns that are being raised as the popularity of electronic cigarettes (e-cigarettes) has soared. In the process, we show the potential benefits to society of translating epidemiologic findings into public health policy.

Kandel, E. and Kandel, D. (2014). Shattuck lecture - A molecular basis for nicotine as a gateway drug. The New England Journal of Medicine, 317(1), 932-943.


Previous use of alcohol, cigarettes, and marijuana and subsequent abuse of prescription opioids in young adults

Purpose. There has been an increase in the abuse of prescription opioids, especially in younger individuals. The current study explores the association between alcohol, cigarette, and/or marijuana use during adolescence and subsequent abuse of prescription opioids during young adulthood. Methods. We used demographic/clinical data from community-dwelling individuals in the 2006-2008 National Survey on Drug Use and Health. We used logistic regression analyses, adjusted for these characteristics, to test whether having previous alcohol, cigarette, or marijuana use was associated with an increased likelihood of subsequently abusing prescription opioids. Results. Twelve percent of the survey population of 18-25 year olds (n6,496) reported current abuse of prescription opioids. For this population, prevalence of previous substance use was 57% for alcohol, 56% for cigarettes, and 34% for marijuana. We found previous alcohol use was associated with the subsequent abuse of prescription opioids in young men but not young women. Among both men and women, previous marijuana use was 2.5 times more likely than no previous marijuana to be associated with subsequent abuse of prescription opioids. We found that among young boys, all previous substance use (alcohol, cigarettes, and marijuana), but only previous marijuana use in young girls, was associated with an increased likelihood of subsequent abuse of prescription opioids during young adulthood. Conclusions. Previous alcohol, cigarette, and marijuana use were each associated with current abuse of prescription opioids in 18-25-year-old men, but only marijuana use was associated with subsequent abuse of prescription opioids in young women. Prevention efforts targeting early substance abuse may help to curb the abuse of prescription opioids.

Fiellin, L. E., Tetrault, J. M., Becker, W. C., Fiellin, D. A., & Hoff, R. A. (2013). Previous use of alcohol, cigarettes, and marijuana and subsequent abuse of prescription opioids in young adultsJournal of Adolescent Health, 52(2), 158-163.


Altered Perception of Reward in Human Cocaine Addiction

People addicted to cocaine have an impaired ability to perceive rewards and exercise control due to disruptions in the brain's reward and control circuits, according to a series of brain-mapping studies and neuropsychological tests conducted at the US Department of Energy's Brookhaven National Laboratory.

Brookhaven National Laboratory. (2006). Altered perception of reward in human cocaine addictionScienceDaily


Rates of Drug Use

Adolescents' perceptions of risks and benefits of conventional cigarettes, e-cigarettes, and marijuana: a qualitative analysis

Purpose. Although rates of adolescent cigarette use have remained constant or decreased, rates of marijuana and e-cigarette use are rising. Knowledge and perceptions of risks and benefits of tobacco products impact adolescents' decisions to use these products. However, little is known regarding adolescents' knowledge and perceptions of risks of e-cigarettes and marijuana nor how these perceptions are formed. This study uses qualitative techniques to assess and compare adolescents' perceptions of the risks and benefits of cigarettes, e-cigarettes, and marijuana. Methods. Twenty-four adolescents (nine females and 15 males) from Northern California participated in six small-group discussions. Adolescents were asked what good or bad things might happen from using these products. To assess how perceptions and knowledge of risks and benefits were formed, participants were asked where and from whom they had learned about these products. Results. Adolescents described negative consequences of cigarette use but were much less sure regarding risks of marijuana and e-cigarette use. Conversely, they described few benefits of cigarettes but described a number of benefits of e-cigarette and marijuana use. Adolescents described learning about these products from the media, from family and friends, and from the school environment. Conclusions.Adolescents have learned from multiple sources about risks of using cigarettes, but they receive much less and often incorrect information regarding marijuana and e-cigarettes, likely resulting in their positive and often ambivalent perceptions of marijuana and e-cigarettes.

Roditis, M. L. & Halpern-Felsher, B. (2015). Adolescents' perceptions of risks and benefits of conventional cigarettes, e-cigarettes, and marijuana: a qualitative analysisJournal of Adolescent Health, 57(2), 179-185.


Adolescents' access to their own prescription medications in the home

Purpose. The objective of this descriptive study was to determine adolescents' access to their own medications at home, specifically prescription pain, stimulant, antianxiety, and sedative medications. Methods. Semistructured interviews were conducted with a cohort of 501 adolescents from two southeastern Michigan school districts. Participants were asked what medications had been prescribed to them during the previous 6 months; if they had received prescription medications, they were asked in-depth questions about them, including how medications were stored and supervised at home. Results. The sample was comprised of adolescents in the 8th and 9th grades, and 50.9% were male. Participants were primarily white (72.9%, n = 365) or African-American (21.6%, n = 108). Slightly less than half of the adolescents (45.9%, n = 230) reported having been prescribed medications in the previous 6 months. Of this group, 14.3% (n = 33) had been prescribed pain medications, 9.6% (n = 22) stimulants, 1.7% (n = 4) antianxiety medications, and .9% (n = 2) sedatives. In total, 57 adolescents were prescribed medications in the pain, stimulant, antianxiety, or sedative categories (including controlled medications), and the majority (73.7%, n = 42) reported that they had unsupervised access to medications with abuse potential. Conclusions. The majority of adolescents who were prescribed medications in the pain, stimulant, antianxiety, or sedative categories during the previous 6 months had unsupervised access to them at home. It is critical that clinicians educate parents and patients about the importance of proper storage and disposal of medications, particularly those with abuse potential.

Ross-Durow, P. L., McCabe, S. E., & Boyd, C. J. (2013). Adolescents' access to their own prescription medications in the homeJournal of Adolescent Health, 53(2), 260-264.


Monitoring the Future is a nationally representative self-report survey on behaviors, attitudes, and values of American secondary school students (in 8th, 10th, and 12th grades), college students, and young adults.


Substance Abuse and Mental Health Services Administration's National Survey on Drug Use and Health is a nationally representative self-report survey that provides national and state-level data on the use of tobacco, alcohol, illicit drugs (including non-medical use of prescription drugs) and mental health in the United States.


Parental Influence

Peer drug use and adolescent polysubstance use: do parenting and school factors moderate this association?

Aims: This study examined the association between peer drug use and adolescent polysubstance use, and investigated if this association was moderated by parenting and/or school factors.

Methods: The sample consisted of 9966 participants (mean age=14.3; 49.34% males) randomly selected from secondary schools in Victoria, Australia. Three 30-day polysubstance use profiles were derived from latent class analysis - no drug use (47.7%), mainly alcohol use (44.1%) and polysubstance use (8.2%). These profiles were then regressed on peer's drug use, family conflict, parental monitoring, parental disapproval of drug use, school commitment, reward for prosocial involvement in school and academic failure, and the interactions between peer's drug use and each of the parenting and school variables.

Results: Relative to non-users, peer's drug use was strongly associated with polysubstance use (OR=30.91, p<0.001), and this association was moderated by parental disapproval of drug use (OR=0.46, p<0.001). This indicated that high level of parental disapproval may mitigate the negative influence of drug using peers. School commitment and parental monitoring were significantly associated with reduced likelihood of polysubstance use (p<0.05), but they did not moderate the relationship between peer drug use and adolescent polysubstance use. All analyses were adjusted for key demographic factors such as age, gender, areas of residence, birth place and family affluence.

Conclusion: Reinforcing parent disapproval of drug use may be an important strategy in reducing adolescent substance use. Parents may need to be more integrated into mainstream prevention programs.

Chan, G. C., Kelly, A. B., Carroll, A., & Williams, J. W. (2017). Peer drug use and adolescent polysubstance use: do parenting and school factors moderate this association? Addictive Behaviors, 64, 78-81. 


Pathways to adolescent alcohol use: family environment, peer influence, and parental expectations

Purpose: This study was conducted to examine the relationships among family environment, peer influence, stress, self-efficacy, and adolescent alcohol use and to test for the potential moderating effects of parental expectations regarding adolescent alcohol use.

Methods: Data were obtained from questionnaires completed by high school students (n = 2573) participating in a longitudinal study of substance use and other problem behaviors. Variables were lagged across three time points to reflect a causal sequence relating family environment to adolescent alcohol use through self-efficacy, peer influence, and stress. A latent measure of family environment included adolescents' perceptions of parental acceptance, parental monitoring, and communication with parents. The latent measure of peer influence included use of alcohol by same-age peers and friends and friends' approval of alcohol use. Observed scale scores were used for self-efficacy and stress measures, and the latent measure of alcohol behaviors included quantity, frequency, and associated problems.

Results: Structural equation modeling indicated good model fit, chi(2) (144) = 831.69, p < .001, comparative fit index (CFI) = .992, root mean square error of approximation (RMSEA) = .043 (.040, .046). Family environment exerted significant indirect effects on adolescent alcohol use through peer influence, self-efficacy, and stress, and parental expectations significantly moderated all structural paths.

Conclusion: Parental expectations of adolescent alcohol use significantly moderated all structural relationships, and greater parental disapproval was associated with less involvement with friends and peers who use alcohol, less peer influence to use alcohol, greater self-efficacy for avoiding alcohol use, and lower subsequent alcohol use and related problems.

Nash, S. G., McQueen, A., & Bray, J. H. (2005). Pathways to adolescent alcohol use: family environment, peer influence, and parental expectationsJournal of Adolescent Health, 37(1), 19-28.


Does parental disapproval of smoking prevent adolescents from becoming established smokers?

Objective: To evaluate the hypothesis that adolescents are less likely to smoke if their parents voice strong disapproval of smoking.

Design and Setting: Three-wave school-based cohort study of rural Vermont adolescents attending 3 K-12 schools. We evaluate cross-sectional and longitudinal associations between perceived parental disapproval of smoking and the adoption of smoking behavior.

Outcome Measures: Students' perceptions of their parents' reaction to their own smoking was ascertained by asking the following question for mothers and fathers: "How do you think your mother (father) would react if you were smoking cigarettes and she (he) knew about it?" A response of "S/he would tell me to stop and be very upset" was considered to indicate strong parental disapproval. Outcome measures include a 6-level smoking index for cross-sectional analyses and, for a longitudinal analysis of 372 never smokers at baseline, being an established smoker (smoked > or =100 cigarettes lifetime and within the past 30 days) by survey 3.

Results: The study samples for the cross-sectional analyses were 662 (baseline), 758 (year 2), and 730 (year 3). Students were equally distributed across grade (4th-11th grades) and gender. At baseline, most (65.9%) adolescents perceived both parents as disapproving of smoking, with 110 (16.6) perceiving 1 parent as disapproving, and 116 (17.5%) perceiving neither parent as disapproving. Perceived disapproval of smoking was inversely associated with adolescent smoking, grade in school, parental and sibling smoking, friend smoking, and ownership of tobacco promotional items. After controlling for confounding influences, adolescents who perceived strong parental disapproval of their smoking were less than half as likely to have higher smoking index levels compared with those who did not perceive strong parental disapproval. In the longitudinal sample of baseline never smokers, those who perceived strong disapproval in both parents at baseline were less than half as likely to become established smokers (adjusted odds ratio 0.4 [0.1, 1.0]). Those who perceived their parents becoming more lenient over time were significantly more likely to progress to established smokers. In all analyses, the effect of parental disapproval of smoking was stronger and more robust than the effect of parent smoking. In addition, the effect of parent disapproval was as strong for parents who smoked as it was for nonsmoking parents. An interaction analysis suggests that the peer smoking effect is attenuated when both parents strongly disapprove of smoking, suggesting that parent disapproval makes adolescents more resistant to the influence of peer smoking.

Conclusions: These findings contrast with the widespread notion that there is little parents can do to prevent their adolescents from becoming smokers. Instead, adolescents who perceive that both parents would respond negatively and be upset by their smoking are less likely to smoke. Interventions that enhance parental self-efficacy in conveying and enforcing no-smoking policies for their children could reduce adolescent smoking.

Sargent, J. D., & Dalton, M. (2001). Does parental disapproval of smoking prevent adolescents from becoming established smokers? Pediatrics, 108(6), 1256-1262.


Parental influence on substance use in adolescent social networks

Objectives: Both peer and parental influences have been associated with the use of addictive substances in adolescence. We evaluated the relationship between the parenting style of an adolescent’s peers’ parents and an adolescent’s substance use.

Design: Longitudinal survey.

Setting: Adolescents across the United States were interviewed at school and at home.

Participants: Nationally representative sample of adolescents in the United States.

Main Exposure: Authoritative versus neglectful parenting style of adolescent’s parents and adolescent’s friends parents; adolescent substance use.

Main Outcome Measures: Adolescent alcohol abuse, smoking, marijuana use, and binge drinking.

Results: If an adolescent has a friend whose mother is authoritative, that adolescent is 40% (95% CI 12%–58%) less likely to drink to the point of drunkenness, 38% (95% CI 5%–59%) less likely to binge drink, 39% (95% CI 12%–58%) less likely to smoke cigarettes, and 43% (95% CI 1%–67%) less likely to use marijuana than an adolescent whose friend’s mother is neglectful, controlling for the parenting style of the adolescent’s own mother, school level fixed effects, and demographics. These results are only partially mediated by peer substance use.

Conclusion: Social network influences may extend beyond the homogeneous dimensions of own-peer or own-parent to include extra-dyadic influences of the wider network. The value of parenting interventions should be re-assessed to take into account these spillover effects in the greater network.

Shakya, H. B., Christakis, N. A., & Fowler, J. H. (2012). Parental influence on substance use in adolescent social networksArchives of Pediatrics & Adolescent Medicine, 166(12), 1132-1139.


Drug Use and Academics

The academic consequences of marijuana use during college

Although several studies have shown that marijuana use can adversely affect academic achievement among adolescents, less research has focused on its impact on postsecondary educational outcomes. This study utilized data from a large longitudinal cohort study of college students to test the direct and indirect effects of marijuana use on college grade point average (GPA) and time to graduation, with skipping class as a mediator of these outcomes. A structural equation model was evaluated taking into account a variety of baseline risk and protective factors (i.e., demographics, college engagement, psychological functioning, alcohol and other drug use) thought to contribute to college academic outcomes. The results showed a significant path from baseline marijuana use frequency to skipping more classes at baseline to lower first-semester GPA to longer time to graduation. Baseline measures of other drug use and alcohol quantity exhibited similar indirect effects on GPA and graduation time. Over time, the rate of change in marijuana use was negatively associated with rate of change in GPA, but did not account for any additional variance in graduation time. Percentage of classes skipped was negatively associated with GPA at baseline and over time. Thus, even accounting for demographics and other factors, marijuana use adversely affected college academic outcomes, both directly and indirectly through poorer class attendance. Results extend prior research by showing that marijuana use during college can be a barrier to academic achievement. Prevention and early intervention might be important components of a comprehensive strategy for promoting postsecondary academic achievement.

Arria, A. M., Caldeira, K. M., Bugbee, B. A., Vincent, K. B., & O'Grady, K. E. (2015). The academic consequences of marijuana use during collegePsychology of Addictive Behaviors, 29(3), 564-575.


Predicting young adult degree attainment by late adolescent marijuana use

Abstract: Purpose. The purpose of this study was to assess whether infrequent and frequent marijuana use at age 19/20 years predicts receipt of educational degrees by the mid-20s, independent of confounding age 18 adolescent risk factors. Methods. Data were from the Monitoring the Future study, an annual nationally representative survey of high school seniors followed into adulthood. Thirteen cohorts (1990-2002) of high school seniors were followed longitudinally to their mid-20s (n = 4,925; 54% female). We used logistic regression and propensity score matching with successive inclusion of age 18 risk factors and substance use to compare age 19/20 frequent marijuana users (six or more occasions in past 30 days) to nonusers, frequent users to infrequent users (1-6 occasions), and infrequent users to nonusers on their likelihood of degree attainment by the mid-20s. Results. Frequent marijuana users were less likely than infrequent users and nonusers to earn bachelor's degrees, even after controlling for a host of age 18 risk factors (e.g., family socioeconomic background, academic performance, educational expectations, truancy). However, these differences were reduced in magnitude to statistical nonsignificance when we controlled for age 18 substance use. Across analyses, the proportion reaching this educational milestone did not differ significantly between infrequent users and nonusers. Conclusions. Results support a growing body of work suggesting that frequent marijuana use predicts a lower likelihood of postsecondary educational attainment, and this difference may originate during secondary school.

Maggs, J. L., Staff, J., Kloska, D. D., Patrick, M. E., O'Malley, P. M., & Schulenberg, J. (2015). Predicting young adult degree attainment by late adolescent marijuana useJournal of Adolescent Health, 57(2), 205-211.


The Academic Opportunity Costs of Substance Use During College. 

A report from the Center on Young Adult Health and Development at the University of Maryland highlights research that shows a clear relationship between substance use and academic performance during college. Strategies aimed at reducing the rates of excessive drinking and drug use among college students could have profound impacts on student retention and could positively impact their long-term success and employability.

Arria, A. M., Caldeira, K. M., Bugbee, B. A., Vincent, K. B., & O'Grady, K. E. (2013). The Academic Opportunity Costs of Substance Use During College. College Park, MD: Center on Young Adult Health and Development.


AMERICA'S DROPOUT CRISIS: THE UNRECOGNIZED CONNECTION TO ADOLESCENT SUBSTANCE USE

Lower high school grades and motivation and higher risk of dropping out are associated with use of illegal substances. This report from the Institute for Behavior and Health discusses decades of scientific studies that show the connection between adolescent substance use and school failure.

DuPont, R. L., Caldeira, K. M., DuPont, H. S., Vincent, K. B., Shea, C. S., & Arria, A. M. (2013). America's Dropout Crisis: The Unrecognized Connection to Adolescent Substance Use. Rockville, MD: Institute for Behavior and Health, Inc.


Drug use patterns and continuous enrollment in college: results from a longitudinal study

Abstract: Objective. Few longitudinal studies have examined the relationship between illicit drug use and academic outcomes among college students. This study characterized drug use patterns of a cohort of young adults who were originally enrolled as first-time, first-year college students in a longitudinal study. It evaluated the association between these drug use patterns and continuous enrollment during college, holding constant demographic characteristics, high school grade point average, fraternity/sorority involvement, personality/temperament characteristics, nicotine dependence, and alcohol use disorder. Method. Participants (n = 1,133; 47% male) were purposively selected from one university and interviewed annually for 4 years, beginning with their first year of college, regardless of continued college attendance. Enrollment data were culled from administrative records. Group-based trajectory analyses characterized 4-year longitudinal drug use patterns. Two grouping variables were derived based on (a) marijuana use frequency and (b) number of illicit drugs used other than marijuana. Seventy-one percent of the sample was continuously enrolled in the home institution during the first 4 years of study. Results. Multivariable logistic regression models demonstrated that infrequent, increasing, and chronic/heavy marijuana use patterns were significantly associated with discontinuous enrollment (adjusted odds ratio = 1.66, 1.74, and 1.99, respectively), compared with minimal use, holding constant covariates. In separate models, drug use other than marijuana also was significantly associated with discontinuous enrollment. Conclusions. Marijuana use and other illicit drug use are both associated with a decreased likelihood of continuous enrollment in college, independent of several other possible risk factors. These findings highlight the need for early intervention with illicit drug users to mitigate possible negative academic consequences.

Arria, A. M., Garnier-Dykstra, L. M., Caldeira, K. M., Vincent, K. B., Winick, E. R., Y O'Grady, K. E. (2013). Drug use patterns and continuous enrollment in college: results from a longitudinal study. Journal of Studies on Alcohol and Drugs, 74(1),71-83.


Dispelling the myth of "smart drugs": cannabis and alcohol use problems predict nonmedical use of prescription stimulants for studying

 This study tested the hypothesis that college students' substance use problems would predict increases in skipping classes and declining academic performance, and that nonmedical use of prescription stimulants (NPS) for studying would occur in association with this decline. A cohort of 984 students in the College Life Study at a large public university in the US participated in a longitudinal prospective study. Interviewers assessed NPS; Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) cannabis and alcohol use disorders; and frequency of skipping class. Semester grade point average (GPA) was obtained from the university. Control variables were race, sex, family income, high school GPA, and self-reported attention deficit hyperactivity disorder diagnosis. Longitudinal growth curve modeling of four annual data waves estimated the associations among the rates of change of cannabis use disorder, percentage of classes skipped, and semester GPA. The associations between these trajectories with NPS for studying was then evaluated. A second structural model substituted alcohol use disorder for cannabis use disorder. More than one-third (38%) reported NPS for studying at least once by Year 4. Increases in skipping class were associated with both alcohol and cannabis use disorder, which were associated with declining GPA. The hypothesized relationships between these trajectories and NPS for studying were confirmed. These longitudinal findings suggest that escalation of substance use problems during college is related to increases in skipping class and to declining academic performance. NPS for studying is associated with academic difficulties. Although additional research is needed to investigate causal pathways, these results suggest that nonmedical users of prescription stimulants could benefit from a comprehensive drug and alcohol assessment to possibly mitigate future academic declines.

Arria, A. M., Wilcox, H. C., Caldeira, K. M., Vincent, K. B., Garnier-Dykstra, L. M., & O'Grady, K. E. (2013). Dispelling the myth of "smart drugs": cannabis and alcohol use problems predict nonmedical use of prescription stimulants for studying. Addictive Behaviors, 38(3), 1643-1650. Research Brief.


School achievement in 14-year-old youths prenatally exposed to marijuana

Abstract: The relation between prenatal marijuana exposure (PME) and school achievement was evaluated in a sample of 524 14-year-olds. Women were recruited during pregnancy and assessed, along with their offspring, at multiple phases from infancy to early adulthood. The sample represents a low-income population. Half of the adolescents are male and 55% are African American. School achievement was assessed with the Wechsler Individual Achievement Test (WIAT) Screener (Psychological Corporation, 1992). A significant negative relation was found between PME and 14-year WIAT composite and reading scores. The deficit in school achievement was mediated by the effects of PME on intelligence test performance at age 6, attention problems and depression symptoms at age 10, and early initiation of marijuana use. These findings suggest that the effects of PME on adolescent achievement are mediated by the earlier negative effects of PME on child characteristics. The negative impact of these characteristics on adolescent achievement may presage later problems in early adulthood.

Goldschmidt, L., Richardson, G. A., Willford, J. A., Severtson, S. G., & Day, N. L. (2012). School achievement in 14-year-old youths prenatally exposed to marijuanaNeurotoxicology and Teratology, 34(1), 161-167.


van Ours, J., & Williams, J. (2007, September 18). Cannabis use and educational attainmentVOX.


The association of ecstasy use and academic achievement among adolescents in two US national surveys

Abstract: The association of ecstasy (3, 4-methylenedioxymethamphetamine, MDMA) use with low academic achievement was examined in two nationally representative surveys of adolescents. We tested whether associations with low academic achievement were of similar magnitude or of stronger magnitude for ecstasy versus marijuana use (without ecstasy use), alcohol/tobacco use (without other drug use) and non-drug use in adolescence. Data from the adolescents in the 2002-2005 National Survey of Drug Use and Health (NSDUH, n= 65,294) and from the 2001-2003 Youth Risk Behavior Survey (YRBS, n= 27,592) were analyzed via weighted logistic regression models. Ecstasy, marijuana, and alcohol/tobacco use were associated with moderate and low academic achievement among adolescents in both surveys. Moreover, ecstasy was more strongly associated with low academic achievement and reporting that school gave no grades than alcohol/tobacco in both samples and than marijuana (NSDUH sample only). Prevention programs should inform adolescents that ecstasy use might impair their academic achievement.

Martins, S.S., & Alexandre, P.K. (2009). The association of ecstasy use and academic achievement among adolescents in two US national surveysAddictive Behaviors, 34(1), 9-16.


The effects of adolescent cannabis use on educational attainment: A review

This paper reviews research examining the link between cannabis use and educational attainment among youth. Cross-sectional studies have revealed significant associations between cannabis use and a range of measures of educational performance including lower grade point average, less satisfaction with school, negative attitudes to school, increased rates of school absenteeism and poor school performance. However, results of cross-sectional studies cannot be used to determine whether cannabis use causes poor educational performance, poor educational performance is a cause of cannabis use or whether both outcomes are a reflection of common risk factors. Nonetheless, a number of prospective longitudinal studies have indicated that early cannabis use may significantly increase risks of subsequent poor school performance and, in particular, early school leaving. This association has remained after control for a wide range of prospectively assessed covariates. Possible mechanisms underlying an association between early cannabis use and educational attainment include the possibility that cannabis use induces an 'amotivational syndrome' or that cannabis use causes cognitive impairment. However, there appears to be relatively little empirical support for these hypotheses. It is proposed that the link between early cannabis use and educational attainment arises because of the social context within which cannabis is used. In particular, early cannabis use appears to be associated with the adoption of an anti-conventional lifestyle characterized by affiliations with delinquent and substance using peers, and the precocious adoption of adult roles including early school leaving, leaving the parental home and early parenthood.

Lynskey, M., & Hall, W. (2000). The effects of adolescent cannabis use on educational attainment: A reviewAddiction, 9(5), 1621-1630.


Does early drug use increase the risk of dropping out of high school

This study examines the impact of early adolescent drug use on subsequent dropping out of high school in a sample of 4,390 adolescents from California and Oregon. Participants were initially surveyed in 7th grade in 1985 and again in 1990 when they should have completed 12th grade. Logistic regression analyses show that frequency of cigarette use during 7th grade predicts dropping out of high school, controlling for demographics, family structure, academic orientation, early deviance, and school environment. Separate analyses by race/ethnicity replicate this finding for Asians, Blacks, and whites, but not for Latinos. For Latinos, early marijuana use predicts dropping out. The results suggest that preventing or reducing the incidence of early smoking and marijuana use may help reduce the probability of dropping out of high school.

Ellickson, P. L., Bui, K., Bell, R., & McGuigan, K. (1998). Does early drug use increase the risk of dropping out of high school. Journal of Drug Issues, 28(2), 357-380.


Consequences of receipt of a psychiatric diagnosis for completion of college

Abstract: The purpose of this study was to evaluate the independent associations between DSM-IV psychiatric disorders and the failure to complete college among college entrants. Methods. Data were from the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). The sample included 15,800 adults, aged 22 years and older, who at least entered college. Diagnoses were made with the NESARC survey instrument, the Alcohol Use Disorder and Associated Disability Interview Schedule-DSM-IV Version. The large sample permitted analysis of multiple psychiatric disorders in the same multivariable logistic regression models. Given the frequent comorbidity of these disorders, this approach is an important step toward disentangling the independent roles of disorders in postsecondary educational outcomes. Results. Evaluation of the independent associations between specific psychiatric disorders and postsecondary educational attainment showed that five diagnoses were positively and significantly associated with the failure to graduate from college. Four were axis I diagnoses: bipolar I disorder, marijuana use disorder, amphetamine use disorder, and cocaine use disorder. One was an axis II diagnosis: antisocial personality disorder. Conclusions. This study provides new data on DSM-IV diagnoses associated with the failure to complete postsecondary education. The findings suggest that psychiatric factors play a significant role in college academic performance, and the benefits of prevention, detection, and treatment of psychiatric illness may therefore include higher college graduation rates.

Hunt, J., Eisenberg, D., & Kilbourne, A. M. (2010). Consequences of receipt of a psychiatric diagnosis for completion of collegePsychiatric Services, 61(4), 399-404.


Marijuana exposure opportunity and initiation during college: Parent and peer influence

Abstract: Marijuana is the most prevalent illicit drug used by adolescents and young adults, yet marijuana initiation is rarely studied past adolescence. The present study sought to advance our understanding of parent and peer influences on marijuana exposure opportunity and incident use during college. A sample of 1,253 students was assessed annually for 4 years starting with the summer prior to college entry. More than one-third (38%(wt)) of students had already used marijuana at least once prior to college entry; another 25%(wt) initiated use after starting college. Of the 360 students who did not use marijuana prior to college, 74% were offered marijuana during college; of these individuals, 54% initiated marijuana use. Both low levels of parental monitoring during the last year of high school and a high percentage of marijuana-using peers independently predicted marijuana exposure opportunity during college, holding constant demographics and other factors (AOR_=_0.92, 95% CI_=_0.88-0.96, p_<_.001 and aor_=_1.11, 95% ci_=_1.08-1.14, p_<_.001, respectively). among individuals with exposure opportunity, peer marijuana use (aor_=_1.04, 95% ci_=_1.03-1.05, p_<_.001), but not parental monitoring, was associated with marijuana initiation. results underscore that peer influences operate well into late adolescence and young adulthood and thus suggest the need for innovative peer-focused prevention strategies. parental monitoring during high school appears to influence exposure opportunity in college; thus, parents should be encouraged to sustain rule-setting and communication about adolescent activities and friend selection throughout high school.

Pinchevsky, G. M., Arria, A. M., Caldeira, K. M., Garnier-Dykstra, L. M., Vincent, K. B., & O'Grady, K. (2012). Marijuana exposure opportunity and initiation during college: Parent and peer influencePrevention Science13(1), 43-54.


Marijuana

General Information        Rates of Use        Effects on the Body         Effects on the Brain  

Marijuana and other Drugs                         Effect on Driving            Other Research

 

General Information

Marijuana: A human experiment without informed consent.

The United States is on the threshold of a national experiment, a human experiment that tests the health and safety of marijuana. The first experiments with psychoactive drugs began in the late 19th century, following the extraction and proliferation of active compounds from opium and coca plants. An exponential and unacceptable rise in human behavioral and biological calamities followed and elicited an aggressive response from the medical, legal and legislative communities. Over-the-counter use of heroin, smoked opium, morphine and cocaine died within a few decades in the early 20th century. The "War on Opium" led to a greater than 90% reduction in opium use internationally starting in the early 20th century. Since then, the popularity of illegally obtained heroin and cocaine has risen and fallen with public perception and access, but these heroin excursions affect much smaller populations than at the turn of the 20th century. We will never have an accurate tally of the human, legal and economic anguish that arose from the legal promotion and proliferation of heroin or cocaine in the few decades that these drugs were legally and widely available. Populations currently addicted are relatively small, but the grim consequences persist and are visible.

Madras, B. Marijuana: A human experiment without informed consent. Journal of Global Drug Policy and Practice, 7(1).


Cannabis: A General Survey of its Harmful Effects

Mary Brett has provided Prevent Teen Drug Use with a comprehensive report on the extensive research related to marijuana, including its effects on the cardiovascular system, immune system, reproductive system, mental health and illness, cognitive function, personality, education, and other drug use, among other topics. Mary Brett is a former Vice President of Europe Against Drugs (Erad) and is a founding member and trustee of Cannabis Skunk Sense (CanSS). She is also a member of Prisons and Addictions Forum (PandA) Center for Policy Studies and a member of World Federation Against Drugs.

Brett, M. (2015, January). Cannabis: A General Survey of its Harmful Effects. Report submitted to The Social Justice Policy Group, 2006.


Adverse health effects of marijuana use

A definitive, comprehensive review of the current state of scientific knowledge on marijuana written by the nation's leading drug scientists has been published by the premier medical journal, The New England Journal of Medicine. This article is of historic importance and of great relevance for the current national debate over marijuana policy. Hopefully it will be useful in stemming the tide of a growing public misconception that marijuana is not an addictive drug and that marijuana use is not harmful. It is imperative that this summary of knowledge be shared widely and that specifically it be used to inform policy in the interest of public health and safety. In a commentary from the Institute for Behavior and Health, Robert L. DuPont, MD presents a brief synopsis of the findings from Volkow, et al. (2014) as well as a policy context for these findings.

Volkow, N.D., Baler, R.D., Compton, W. M. & Weiss, S. R. (2014). Adverse health effects of marijuana useNew England Journal of Medicine, 370(23), 2219-2227. 

Institute for Behavior and Health Commentary.


Adverse effects of cannabis

Cannabis is the most widely used illicit drug in many developed societies. Its health and psychological effects are not well understood and remain the subject of much debate, with opinions on its risks polarized along the lines of proponents' views on what its legal status should be. An unfortunate consequence of this polarization of opinion has been the absence of any consensus on what health information the medical profession should give to patients who are users or potential users of cannabis. There is conflicting evidence about many of the effects of cannabis use, so we summarize the evidence on the most probable adverse health and psychological consequences of acute and chronic use. This uncertainty, however, should not prevent medical practitioners from advising patients about the most likely ill-effects of their cannabis use. Here we make some suggestions about the advice doctors can give to patients who use, or are contemplating the use, of this drug.

Hall, W. & Solowij, N. (1998). Adverse effects of cannabisThe Lancet, 352(9140), 1611-1616.


Adverse health effects of non-medical cannabis use

For over two decades, cannabis, commonly known as marijuana, has been the most widely used illicit drug by young people in high-income countries, and has recently become popular on a global scale. Epidemiological research during the past 10 years suggests that regular use of cannabis during adolescence and into adulthood can have adverse effects. Epidemiological, clinical, and laboratory studies have established an association between cannabis use and adverse outcomes. We focus on adverse health effects of greatest potential public health interest-that is, those that are most likely to occur and to affect a large number of cannabis users. The most probable adverse effects include a dependence syndrome, increased risk of motor vehicle crashes, impaired respiratory function, cardiovascular disease, and adverse effects of regular use on adolescent psychosocial development and mental health.

Hall, W., & Degenhardt, L. (2009). Adverse health effects of non-medical cannabis useThe Lancet, 374, 1383–1391.


Young adult sequelae of adolescent cannabis use: an integrative analysis

Background. Debate continues about the consequences of adolescent cannabis use. Existing data are limited in statistical power to examine rarer outcomes and less common, heavier patterns of cannabis use than those already investigated; furthermore, evidence has a piecemeal approach to reporting of young adult sequelae. We aimed to provide a broad picture of the psychosocial sequelae of adolescent cannabis use. Methods. We integrated participant-level data from three large, long-running longitudinal studies from Australia and New Zealand: the Australian Temperament Project, the Christchurch Health and Development Study, and the Victorian Adolescent Health Cohort Study. We investigated the association between the maximum frequency of cannabis use before age 17 years (never, less than monthly, monthly or more, weekly or more, or daily) and seven developmental outcomes assessed up to age 30 years (high-school completion, attainment of university degree, cannabis dependence, use of other illicit drugs, suicide attempt, depression, and welfare dependence). The number of participants varied by outcome (N=2537 to N=3765). Findings. We recorded clear and consistent associations and dose-response relations between the frequency of adolescent cannabis use and all adverse young adult outcomes. After covariate adjustment, compared with individuals who had never used cannabis, those who were daily users before age 17 years had clear reductions in the odds of high-school completion (adjusted odds ratio 0•37, 95% CI 0•20-0•66) and degree attainment (0•38, 0•22-0•66), and substantially increased odds of later cannabis dependence (17•95, 9•44-34•12), use of other illicit drugs (7•80, 4•46-13•63), and suicide attempt (6•83, 2•04-22•90). Interpretation. Adverse sequelae of adolescent cannabis use are wide ranging and extend into young adulthood. Prevention or delay of cannabis use in adolescence is likely to have broad health and social benefits. Efforts to reform cannabis legislation should be carefully assessed to ensure they reduce adolescent cannabis use and prevent potentially adverse developmental effects.

Silins, E., Horwood, L. J., Patton, G. C., Fergusson, D. M., Olsson, C. A., Hutchinson, D. M., et al. (2014). Young adult sequelae of adolescent cannabis use: an integrative analysisThe Lancet, 1(4), 286-293.


Rates and Patterns of Marijuana Use

Adolescents' use of medical marijuana: a secondary analysis of Monitoring the Future data

Purpose. To examine adolescents' annual use of medical marijuana and determine if legal medical marijuana users are at lower risk for frequent marijuana use and other substance use when compared to adolescents who use diverted medical marijuana or from an illicit source. Methods. Public access Monitoring the Future data were used for this secondary analysis. The total weighted sample size was 4394 12th graders. Results. Users of medical marijuana and diverted medical marijuana had notable odds of using daily, using prescription drugs, and using illicit drugs among other substance use behaviors. Medical marijuana users had much higher odds of using medical marijuana because of being "hooked" when compared to diverted medical users and illicit users. Conclusion. This study is the first to provide nationally representative data on three groups of adolescent marijuana users. Although most adolescents use illicit sources, more adolescents appear to be using diverted medical marijuana, than using medical marijuana legally.

Boyd, C. J., Veliiz, P. T., & McCabe, S. E. (2015). Adolescents' use of medical marijuana: a secondary analysis of Monitoring the Future dataJournal of Adolescent Health, 57(2), 241-244.


Medical marijuana laws in 50 states: investigating the relationship between state legalization of medical marijuana and marijuana use, abuse and dependence.

Background. Marijuana is the most frequently used illicit substance in the United States. Little is known of the role that macro-level factors, including community norms and laws related to substance use, play in determining marijuana use, abuse and dependence. We tested the relationship between state-level legalization of medical marijuana and marijuana use, abuse, and dependence. Methods. We used the second wave of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a national survey of adults aged 18+ (n=34,653). Selected analyses were replicated using the National Survey on Drug Use and Health (NSDUH), a yearly survey of ~68,000 individuals aged 12+. We measured past-year cannabis use and DSM-IV abuse/dependence. Results. In NESARC, residents of states with medical marijuana laws had higher odds of marijuana use (OR: 1.92; 95% CI: 1.49-2.47) and marijuana abuse/dependence (OR: 1.81; 95% CI: 1.22-2.67) than residents of states without such laws. Marijuana abuse/dependence was not more prevalent among marijuana users in these states (OR: 1.03; 95% CI: 0.67-1.60), suggesting that the higher risk for marijuana abuse/dependence in these states was accounted for by higher rates of use. In NSDUH, states that legalized medical marijuana also had higher rates of marijuana use. Conclusions.States that legalized medical marijuana had higher rates of marijuana use. Future research needs to examine whether the association is causal, or is due to an underlying common cause, such as community norms supportive of the legalization of medical marijuana and of marijuana use.

Cerdá M, Wall M, Keyes KM, Galea S, & Hasin D. (2012). Medical marijuana laws in 50 states: investigating the relationship between state legalization of medical marijuana and marijuana use, abuse and dependence. Drug and Alcohol Dependence, 120(1-3), 22-27.


Medical marijuana use among adolescents in substance abuse treatment

Objective. To assess the prevalence and frequency of medical marijuana diversion and use among adolescents in substance abuse treatment and to identify factors related to their medical marijuana use. Method. This study calculated the prevalence and frequency of diverted medical marijuana use among adolescents (n = 164), ages 14-18 years (mean age = 16.09, SD = 1.12), in substance abuse treatment in the Denver metropolitan area. Bivariate and multivariate analyses were completed to determine factors related to adolescents' use of medical marijuana. Results. Approximately 74% of the adolescents had used someone else's medical marijuana, and they reported using diverted medical marijuana a median of 50 times. After adjusting for gender and race/ethnicity, adolescents who used medical marijuana had an earlier age of regular marijuana use, more marijuana abuse and dependence symptoms, and more conduct disorder symptoms compared with those who did not use medical marijuana. Conclusions. Medical marijuana use among adolescent patients in substance abuse treatment is very common, implying substantial diversion from registered users. These results support the need for policy changes that protect against diversion of medical marijuana and reduce adolescent access to diverted medical marijuana. Future studies should examine patterns of medical marijuana diversion and use in general population adolescents.

Salomonsen-Sautel, S., Sakai, J.T., Thurstone, C., Corley, R., & Hopfer, C. (2012). Medical marijuana use among adolescents in substance abuse treatmentJournal of the American Academy of Child and Adolescent Psychiatry, 51(7), 694-702.


Marijuana's Effects on the Body

Cannabis use: signal of increasing risk of serious cardiovascular disorders.

Background. Cannabis is known to be associated with neuropsychiatric problems, but less is known about complications affecting other specified body systems. We report and analyze 35 recent remarkable cardiovascular complications following cannabis use. Methods and Results. In France, serious cases of abuse and dependence in response to the use of psychoactive substances must be reported to the national system of the French Addictovigilance Network. We identified all spontaneous reports of cardiovascular complications related to cannabis use collected by the French Addictovigilance Network from 2006 to 2010. We described the clinical characteristics of these cases and their evolution: 1.8% of all cannabis-related reports (35/1979) were cardiovascular complications, with patients being mostly men (85.7%) and of an average age of 34.3 years. There were 22 cardiac complications (20 acute coronary syndromes), 10 peripheral complications (lower limb or juvenile arteriopathies and Buerger-like diseases), and 3 cerebral complications (acute cerebral angiopathy, transient cortical blindness, and spasm of cerebral artery). In 9 cases, the event led to patient death. Conclusions. Increased reporting of cardiovascular complications related to cannabis and their extreme seriousness (with a death rate of 25.6%) indicate cannabis as a possible risk factor for cardiovascular disease in young adults, in line with previous findings. Given that cannabis is perceived to be harmless by the general public and that legalization of its use is debated, data concerning its danger must be widely disseminated. Practitioners should be aware that cannabis may be a potential triggering factor for cardiovascular complications in young people.

Jouanjus, E., Lapeyre-Mestre, M., & Micallef, J. (2014). Cannabis use: signal of increasing risk of serious cardiovascular disorders. Journal of the American Heart Association, 3, e000638.


Bullous lung disease due to marijuana

Background and Objective. In contrast to the well-described effects of tobacco smoking upon pulmonary emphysema, with approximately 15% of smokers being affected at the age of 65 years, the effects of marijuana smoking are rarely reported and poorly understood. Methods. We report a series of 10 patients (mean age 41 +/- 9 years, eight male, two female), who presented over a period of 12 months to our respiratory unit with new respiratory symptoms, and who admitted to regular chronic marijuana smoking (>1 year continuously). Symptoms on presentation were dyspnoea (n = 4), pneumothorax (n = 4) and chest infection (n = 2). Results. High-resolution CT revealed asymmetrical, variably sized, emphysematous bullae in the upper and mid zones. However, the CXR was normal in four patients and lung function was normal in five. Conclusions. Marijuana smoking leads to asymmetrical bullous disease, often in the setting of normal CXR and lung function. In subjects who smoke marijuana, these pathological changes occur at a younger age (approximately 20 years earlier) than in tobacco smokers.

Hii, S. W., Tam, J. D., Thompson, B. R., & Naughton, M. T. (2008). Bullous lung disease due to marijuanaRespirology, 13(1), 122-127.


The Impact of Cannabis on Your Lungs.

A recent report from the British Lung Foundation reviews what is known about the effects of smoking marijuana: "Current evidence shows that cannabis smoking poses a substantial hazard to our lungs, although we know far less about the effects of cannabis smoke than the effects of tobacco smoke... We recommend that public health education programs be implemented to dispel the myth that smoking cannabis is relatively safe, and to highlight the adverse respiratory effects of smoking cannabis mixed with tobacco." About one third of British people mistakenly believe that smoking marijuana is not harmful to one's health.

British Lung Foundation. (2012). The Impact of Cannabis on Your Lungs. London: British Lung Foundation. 


Marijuana's Effects on the Brain

Structural and Functional Imaging Studies in Chronic Cannabis Users: A Systematic Review of Adolescent and Adult Findings

Background. The growing concern about cannabis use, the most commonly used illicit drug worldwide, has led to a significant increase in the number of human studies using neuroimaging techniques to determine the effect of cannabis on brain structure and function. We conducted a systematic review to assess the evidence of the impact of chronic cannabis use on brain structure and function in adults and adolescents. Methods. Papers published until August 2012 were included from EMBASE, Medline, PubMed and LILACS databases following a comprehensive search strategy and pre-determined set of criteria for article selection. Only neuroimaging studies involving chronic cannabis users with a matched control group were considered. Results.One hundred and forty-two studies were identified, of which 43 met the established criteria. Eight studies were in adolescent population. Neuroimaging studies provide evidence of morphological brain alterations in both population groups, particularly in the medial temporal and frontal cortices, as well as the cerebellum. These effects may be related to the amount of cannabis exposure. Functional neuroimaging studies suggest different patterns of resting global and brain activity during the performance of several cognitive tasks both in adolescents and adults, which may indicate compensatory effects in response to chronic cannabis exposure. Limitations. However, the results pointed out methodological limitations of the work conducted to date and considerable heterogeneity in the findings. Conclusion. Chronic cannabis use may alter brain structure and function in adult and adolescent population. Further studies should consider the use of convergent methodology, prospective large samples involving adolescent to adulthood subjects, and data-sharing initiatives.

Batalla, A., Bhattacharyya, S., Yücel, M., Fusar-Poli, P., Crippa, J. A., et al. (2013). Structural and functional imaging studies in chronic cannabis users: a systematic review of adolescent and adult findingsPLoS ONE 8(2), e55821.


Persistent cannabis users show neuropsychological decline from childhood to midlife

Recent reports show that fewer adolescents believe that regular cannabis use is harmful to health. Concomitantly, adolescents are initiating cannabis use at younger ages, and more adolescents are using cannabis on a daily basis. The purpose of the present study was to test the association between persistent cannabis use and neuropsychological decline and determine whether decline is concentrated among adolescent-onset cannabis users. Participants were members of the Dunedin Study, a prospective study of a birth cohort of 1,037 individuals followed from birth (1972/1973) to age 38 y. Cannabis use was ascertained in interviews at ages 18, 21, 26, 32, and 38 y. Neuropsychological testing was conducted at age 13 y, before initiation of cannabis use, and again at age 38 y, after a pattern of persistent cannabis use had developed. Persistent cannabis use was associated with neuropsychological decline broadly across domains of functioning, even after controlling for years of education. Informants also reported noticing more cognitive problems for persistent cannabis users. Impairment was concentrated among adolescent-onset cannabis users, with more persistent use associated with greater decline. Further, cessation of cannabis use did not fully restore neuropsychological functioning among adolescent-onset cannabis users. Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.

Meier, M. H., Caspi, A., Ambler, A., Harrington, H., Houts, R., Keefe, R. S., et al. (2012). Persistent cannabis users show neuropsychological decline from childhood to midlifeProceedings of the National Academy of Sciences of the United States of America, 109(40), E2657-E2664.


Age of onset of marijuana use and executive function

Marijuana (MJ) remains the most widely abused illicit substance in the United States, and in recent years, a decline in perceived risk of MJ use has been accompanied by a simultaneous increase in rates of use among adolescents. In this study, the authors hypothesized that chronic MJ smokers would perform cognitive tasks, specifically those that require executive function, more poorly than control subjects and that individuals who started smoking MJ regularly prior to age 16 (early onset) would have more difficulty than those who started after age 16 (late onset). Thirty-four chronic, heavy MJ smokers separated into early and late onset groups, and 28 non-MJ smoking controls completed a battery of neurocognitive measures. As hypothesized, MJ smokers performed more poorly than controls on several measures of executive function. Age of onset analyses revealed that these between-group differences were largely attributed to the early onset group, who were also shown to smoke twice as often and nearly 3 times as much MJ per week relative to the late onset smokers. Age of onset, frequency, and magnitude of MJ use were all shown to impact cognitive performance. Findings suggest that earlier MJ onset is related to poorer cognitive function and increased frequency and magnitude of MJ use relative to later MJ onset. Exposure to MJ during a period of neurodevelopmental vulnerability, such as adolescence, may result in altered brain development and enduring neuropsychological changes.

Gruber, S. A., Sagar, K. A., Dahlgren, M. K., Racine, M., & Lukas, S. E. (2012). Age of onset of marijuana use and executive functionPsychology of Addictive Behaviors : Journal of the Society of Psychologists in Addictive Behaviors26(3), 496–506. 


Triggering myocardial infarction by marijuana.

Background. Marijuana use in the age group prone to coronary artery disease is higher than it was in the past. Smoking marijuana is known to have hemodynamic consequences, including a dose-dependent increase in heart rate, supine hypertension, and postural hypotension; however, whether it can trigger the onset of myocardial infarction is unknown. Methods and Results. In the Determinants of Myocardial Infarction Onset Study, we interviewed 3882 patients (1258 women) with acute myocardial infarction an average of 4 days after infarction onset. We used the case-crossover study design to compare the reported use of marijuana in the hour preceding symptoms of myocardial infarction onset to its expected frequency using self-matched control data. Of the 3882 patients, 124 (3.2%) reported smoking marijuana in the prior year, 37 within 24 hours and 9 within 1 hour of myocardial infarction symptoms. Compared with nonusers, marijuana users were more likely to be men (94% versus 67%, P,0.001), current cigarette smokers (68% versus 32%, P,0.001), and obese (43% versus 32%, P50.008). They were less likely to have a history of angina (12% versus 25%, P,0.001) or hypertension (30% versus 44%, P50.002). The risk of myocardial infarction onset was elevated 4.8 times over baseline (95% confidence interval, 2.4 to 9.5) in the 60 minutes after marijuana use. The elevated risk rapidly decreased thereafter. Conclusions. Smoking marijuana is a rare trigger of acute myocardial infarction. Understanding the mechanism through which marijuana causes infarction may provide insight into the triggering of myocardial infarction by this and other, more common stressors.

Mittleman, M. A., Lewis, R. A., Maclure, M., Sherwood, J. B., & Muller, J. E. (2000). Triggering myocardial infarction by marijuana.Circulation, 103, 2805-2809.


Dose-related neurocognitive effects of marijuana use

Background. Although about 7 million people in the US population use marijuana at least weekly, there is a paucity of scientific data on persistent neurocognitive effects of marijuana use. Objective. To determine if neurocognitive deficits persist in 28-day abstinent heavy marijuana users and if these deficits are dose-related to the number of marijuana joints smoked per week. Methods. A battery of neurocognitive tests was given to 28-day abstinent heavy marijuana abusers. Results. As joints smoked per week increased, performance decreased on tests measuring memory, executive functioning, psychomotor speed, and manual dexterity. When dividing the group into light, middle, and heavy user groups, the heavy group performed significantly below the light group on 5 of 35 measures and the size of the effect ranged from 3.00 to 4.20 SD units. Duration of use had little effect on neurocognitive performance. Conclusions. Very heavy use of marijuana is associated with persistent decrements in neurocognitive performance even after 28 days of abstinence. It is unclear if these decrements will resolve with continued abstinence or become progressively worse with continued heavy marijuana use.

Bolla, K. I., Brown, K., Eldreth, D., Tate, K., & Cadet, J. L. (2002). Dose-related neurocognitive effects of marijuana useNeurology, 59(9), 1337-1374


Early marijuana use related to later illicit drug abuse and dependence

Adults who first started using marijuana at or before the age of 14 are most likely to have abused or been dependent on illicit drugs in the past year, according to data from the National Survey on Drug Use and Health (NSDUH). Adults who first used marijuana at age 14 or younger were six times more likely to meet the criteria for past year illicit drug abuse or dependence than those who first used marijuana when they were 18 or older (12.6% vs. 2.1%) and almost twice as likely as those who started between the ages of 15 and 17 (12.6% vs. 6.6%). Similar results have been found for early alcohol use (see CESAR FAX, Volume 19, Issue 40) and the early non-medical use of prescription drugs (see CESAR FAX, Volume 17, Issue 8).

Center for Substance Abuse Research. (2010, October 25). Early marijuana use related to later illicit drug abuse and dependence. CESAR Fax, 19(11).


Heavy Marijuana Use May Damage Developing Brain In Teens, Young Adults

Adolescents and young adults who are heavy users of marijuana are more likely than non-users to have disrupted brain development, according to a new study. Pediatric researchers found abnormalities in areas of the brain that interconnect brain regions involved in memory, attention, decision-making, language and executive functioning skills. The findings are of particular concern because adolescence is a crucial period for brain development and maturation.

Children's Hospital of Philadelphia. (2009, February 3). Heavy Marijuana Use May Damage Developing Brain In Teens, Young AdultsScienceDaily.


An evidence-based review of acute and long-term effects of cannabis use on executive cognitive functions

Cannabis use has been shown to impair cognitive functions on a number of levels-from basic motor coordination to more complex executive function tasks, such as the ability to plan, organize, solve problems, make decisions, remember, and control emotions and behavior. These deficits differ in severity depending on the quantity, recency, age of onset and duration of marijuana use. Understanding how cannabis use impairs executive function is important. Individuals with cannabis-related impairment in executive functions have been found to have trouble learning and applying the skills required for successful recovery, putting them at increased risk for relapse to cannabis use. Here we review the research on the acute, residual, and long-term effects of cannabis use on executive functions, and discuss the implications for treatment.

Crean, R. D., Crane, N. A., & Mason, B. J. (2011). An evidence-based review of acute and long-term effects of cannabis use on executive cognitive functionsJournal of Addictive Medicine, 5(1), 1-8.


Long-term consequences of adolescent cannabis exposure on the development of cognition, brain structure and function: An overview of animal and human research

Over the last decade there has been a steady increase in the prevalence of frequent cannabis use among teenagers, accompanied by a decrease in age of first use. Evidence from both animal and human studies suggests that the severity of the effects of cannabis use on cognitive development is dependent on the age when cannabis use begins. One possible explanation is that those who begin cannabis use early in adolescence are more likely to become heavily dependent. It is plausible that chronic cannabis abuse will then interfere with educational and vocational training. From a more biological perspective, however, use of cannabis during critical developmental periods in the still maturing brain may induce persistent alterations in brain structure and brain function. Therefore, the effects of frequent cannabis use during adolescence could be different from and more serious than during adulthood, an issue increasingly recognized in the field of cannabis research. In this paper we review the relevant animal and human literature on long-term effects of frequent exposure to cannabis during adolescence on the development of cognition, brain structure and function, and discuss implications, methodological and conceptual issues, and future prospects.

Jager, G., & Ramsey, N. F. (2008). Long-term consequences of adolescent cannabis exposure on the development of cognition, brain structure and function: an overview of animal and human researchCurrent Drug Abuse Reviews, 1(2), 114-123.


Specific attentional dysfunction in adults following early start of cannabis use

Rationale and Objective. The present study tested the hypothesis that chronic interference by cannabis with endogenous cannabinoid systems during peripubertal development causes specific and persistent brain alterations in humans. As an index of cannabinoid action, visual scanning, along with other attentional functions, was chosen. Visual scanning undergoes a major maturation process around age 12-15 years and, in addition, the visual system is known to react specifically and sensitively to cannabinoids. Methods. From 250 individuals consuming cannabis regularly, 99 healthy pure cannabis users were selected. They were free of any other past or present drug abuse, or history of neuropsychiatric disease. After an interview, physical examination, analysis of routine laboratory parameters, plasma/urine analyses for drugs, and MMPI testing, users and respective controls were subjected to a computer-assisted attention test battery comprising visual scanning, alertness, divided attention, flexibility, and working memory. Results. Of the potential predictors of test performance within the user group, including present age, age of onset of cannabis use, degree of acute intoxication (THC+THCOH plasma levels), and cumulative toxicity (estimated total life dose), an early age of onset turned out to be the only predictor, predicting impaired reaction times exclusively in visual scanning. Early-onset users (onset before age 16; n = 48) showed a significant impairment in reaction times in this function, whereas late-onset users (onset after age 16; n = 51) did not differ from controls (n = 49). Conclusions. These data suggest that beginning cannabis use during early adolescence may lead to enduring effects on specific attentional functions in adulthood. Apparently, vulnerable periods during brain development exist that are subject to persistent alterations by interfering exogenous cannabinoids.

Ehrenreich, H., Rinn, T., Kunert, H.J., Moeller, M.R., Poser, W., Schilling, L., Gigerenzer, G., & Hoehe, M.R. (1999). Specific attentional dysfunction in adults following early start of cannabis usePsychopharmacology, 142(3), 295-301.


Early-onset cannabis use and cognitive deficits: What is the nature of the association?

Background. Individuals who initiate cannabis use at an early age, when the brain is still developing, might be more vulnerable to lasting neuropsychological deficits than individuals who begin use later in life. Methods. We analyzed neuropsychological test results from 122 long-term heavy cannabis users and 87 comparison subjects with minimal cannabis exposure, all of whom had undergone a 28-day period of abstinence from cannabis, monitored by daily or every-other-day observed urine samples. We compared early-onset cannabis users with late-onset users and with controls, using linear regression controlling for age, sex, ethnicity, and attributes of family of origin. Results. The 69 early-onset users (who began smoking before age 17) differed significantly from both the 53 late-onset users (who began smoking at age 17 or later) and from the 87 controls on several measures, most notably verbal IQ (VIQ). Few differences were found between late-onset users and controls on the test battery. However, when we adjusted for VIQ, virtually all differences between early-onset users and controls on test measures ceased to be significant. Conclusions. Early-onset cannabis users exhibit poorer cognitive performance than late-onset users or control subjects, especially in VIQ, but the cause of this difference cannot be determined from our data. The difference may reflect (1). innate differences between groups in cognitive ability, antedating first cannabis use; (2). an actual neurotoxic effect of cannabis on the developing brain; or (3). poorer learning of conventional cognitive skills by young cannabis users who have eschewed academics and diverged from the mainstream culture.

Pope Jr., H.G., Gruber, A.J., Hudson, J.I, Cohane, G., Huestis, M.A., & Yurgelun-Todd, D. (2003). Early-onset cannabis use and cognitive deficits: what is the nature of the association? Drug and Alcohol Dependence, 69(3), 303-310.


Changes in hippocampal morphology and neuroplasticity induced by adolescent THC treatment are associated with cognitive impairment in adulthood

Marijuana and hashish are the illicit drugs most frequently used by human adolescents. Given the continued neurodevelopment throughout adolescence, adolescents may be more vulnerable than adults to certain neural consequences of heavy marijuana use. This study aimed to assess whether an experimental model of adolescent chronic exposure to Delta9-tetrahydrocannabinol (THC), may induce lasting effects on learning and memory. Adolescent rats have been treated with THC or its vehicle from 35 to 45 postnatal days (PND) and left undisturbed until their adulthood (75 PND) when aversive and spatial memory was assessed using the passive avoidance and radial maze tasks. No alteration was found in aversive memory, but in the radial maze THC pretreated animals exhibited a worse performance than vehicles, suggesting a deficit in spatial working memory. To correlate memory impairment to altered neuroplasticity, level of marker proteins was investigated in the hippocampus, the most relevant area mediating spatial memory. A significant decrease in the astroglial marker glial fibrillar acid protein was found as well as in pre- and postsynaptic protein expression (VAMP2, PSD95) and NMDA receptor levels in pretreated rats. To parallel these changes to alteration in dendritic morphology, Golgi-Cox staining was performed in the hippocampal dentate gyrus. Pretreated rats had a significantly lower total dendritic length and number than vehicles, as well as reduced spine density. Our data suggest that THC pretreated rats may establish less synaptic contacts and/or less efficient synaptic connections throughout the hippocampus and this could represent the molecular underpinning of the cognitive deficit induced by adolescent THC treatment.

Rubino, T., Realini, N., Braida, D., Guidi, S., Capurro, V., Vigano, D., ... & Parolaro, D. (2009). Changes in hippocampal morphology and neuroplasticity induced by adolescent THC treatment are associated with cognitive impairment in adulthoodHippocampus, 19(8), 763-772.


Brain morphological changes and early marijuana use: A magnetic resonance and positron emission tomography study

Background. The focus of this report is on the possible role that the age of first use of marijuana may play on brain morphology and function. Methods. Magnetic resonance imaging (MRI) and positron emission tomography (PET) were utilized to study 57 subjects. Brain volume measures (whole brain, gray matter, white matter and lateral ventricle volumes), global cerebral blood flow (CBF) and body size were evaluated. Results. There are three primary findings related to age of first use of marijuana. Subjects who started using marijuana before age 17, compared to those who started later, had smaller whole brain and percent cortical gray matter and larger percent white matter volumes. Functionally, males who started using marijuana before 17 had significantly higher CBF than other males. Both males and females who started younger were physically smaller in height and weight, with the effects being greater in males. Conclusions. These findings suggest that the age at which exposure to marijuana begins is important. Early adolescence may be a critical period for effects that are not present when exposure begins later. These results are discussed in light of reported effects of marijuana on gonadal and pituitary hormones.

Wilson, W., Matthew, R., Turkington, T., Hawk, T., Coleman, R. E., & Provenzale, J. (2000). Brain morphological changes and early marijuana use: A magnetic resonance and positron emission tomography studyJournal of Addictive Diseases, 19(1), 1-22.


Marijuana and Other Drug Use

Does cannabis use encourage other forms of illicit drug use

Aims. To examine the relationship between cannabis use in adolescence and the onset of other illicit drug use. Method. Data were gathered over the course of a 21-year longitudinal study of a birth cohort of 1265 New Zealand children. Measures analysed included: (a) frequency of cannabis use and other illicit drugs from 15-21; (b) family, social, educational and behavioural backgrounds of cohort members prior to 15; and (c) adolescent life-style variables. Findings. (i) By 21, nearly 70% of cohort members and used cannabis and 26% had used other illicit drugs. (ii) In all but three cases, the use of cannabis had preceded the use of illicit drugs. (iii) Those using cannabis on more than 50 occasions a year had hazards of other illicit drug use that were 140 times higher than non-users. (iv) After adjustment for covariate factors, including childhood factors, family factors and adolescent life-style factors, cannabis use remained strongly related to the onset of other forms of illicit drug use. Those using cannabis on more than 50 occasions per year had hazards of other illicit drug use that were 59.2 times higher than non-users. Conclusions. Findings support the view that cannabis may act as a gateway drug that encourages other forms of illicit drug use. None the less, the possibility remains that the association is non-causal and reflects factors that were not adequately controlled in the analysis.

Fergusson, D. M., & Horwood, L. J. (2000). Does cannabis use encourage other forms of illicit drug useAddiction, 95(4), 505-520.


Cannabis use stages as predictor of subsequent initiation with other illicit drugs among French adolescents: Use of a multi-state model

The aim of this study was to confirm the influence of cannabis use patterns on the probability of initiation with other illicit drugs (OID). A French nationwide retrospective cohort on drug use was reconstituted on 29,393 teenagers. A Markov multi-state model was fitted, modelling all possible pathways from initial abstinence to cannabis initiation, daily cannabis use and OID initiation. The model was adjusted for tobacco and alcohol use. The risk for OID initiation appeared 21 times higher among cannabis experimenters and 124 times higher among daily cannabis users than among non-users. Tobacco and alcohol use were associated with a greater risk of moving on to cannabis initiation (hazard ratio (HR)=1.2 for tobacco initiation, HR=2.6 for daily tobacco use and HR=2.8 for drunkenness initiation). The results of this study provide a confirmation of a stage process in drug use, mediated by cannabis and liable to lead to OID experiment. This is compatible with the literature on the gateway theory, but goes further by modelling the entire sequence of use. OID experiment could be a consequence of initial opportunity to use the more accessible illicit drug, cannabis.

Mayet, A., Legleye, S., Falissard, B., & Chau, N. (2012). Cannabis use stages as predictor of subsequent initiation with other illicit drugs among French adolescents: use of a multi-state modelAddictive Behaviors, 37(2), 160-166.


A twin study of early cannabis use and subsequent use and abuse/dependence of other illicit drugs.

Introduction. Cannabis use is strongly associated with the use and abuse/dependence of other illicit drugs. Gateway and common liabilities models have been employed to explain this relationship. We sought to examine this association using a combination of the discordant twin design and modeling methods. Method. We assess the relationship between early cannabis use and the subsequent use and abuse/ dependence of other illicit drugs in a population-based sample of male and female twin pairs using four analyses: (i) analysis of the association between early cannabis use and other illicit drug use and abuse/dependence in the entire sample of twins, (ii) assessment of the influence of early cannabis use in twin 1 on twin 2's use or abuse/dependence of other illicit drugs, (iii) use of twin pairs discordant for early cannabis use in a discordant twin design and (iv) a model-fitting procedure. Results. We found: (i) a strong association between early cannabis use and use and abuse/dependence of other illicit drugs in the sample, (ii) twin 1's early cannabis use is significantly associated with the twin 2's other illicit drug use, (iii) the role of correlated genetic factors with some evidence for a causal influence, and (iv) the correlated liabilities model fits the data well. Conclusions. Early cannabis use is strongly associated with other illicit drug use and abuse/dependence. The relationship arises largely due to correlated genetic and environmental influences with persisting evidence for some causal influences.

Agrawal, A., Neale, M. C., Prescott, C. A., & Kendler, K. S. (2004). A twin study of early cannabis use and subsequent use and abuse/dependence of other illicit drugsPsychological Medicine, 34(7), 1227-1237.


Marijuana and Driving

Marijuana use and car crash injury

Aims. To investigate the relationship between marijuana use prior to driving, habitual marijuana use and car crash injury. Design and Setting. Population based case-control study in Auckland, New Zealand. Participants. Case vehicles were all cars involved in crashes in which at least one occupant was hospitalized or killed anywhere in the Auckland region, and control vehicles were a random sample of cars driving on Auckland roads. The drivers of 571 case and 588 control vehicles completed a structured interview. Measurements. Self reported marijuana use in the 3 hours prior to the crash/survey and habitual marijuana use over the previous 12 months were recorded, along with a range of other variables potentially related to crash risk. The main outcome measure was hospitalization or death of a vehicle occupant due to car crash injury. Findings. Acute marijuana use was significantly associated with car crash injury, after controlling for the confounders age, gender, ethnicity, education level, passenger carriage, driving exposure and time of day (OR 3.9, 95% CI 1.2-12.9). However, after adjustment for these confounders plus other risky driving at the time of the crash (blood alcohol concentration, seat-belt use, travelling speed and sleepiness score), the effect of acute marijuana intake was no longer significant (OR 0.8, 95% CI 0.2-3.3). There was a strong significant association between habitual use and car crash injury after adjustment for all the above confounders plus acute use prior to driving (OR 9.5, 95% CI 2.8-32.3). Conclusions. This population-based case-control study indicates that habitual use of marijuana is strongly associated with car crash injury. The nature of the relationship between marijuana use and risk-taking is unclear and needs further research. The prevalence of marijuana use in this driving population was low, and acute use was associated with habitual marijuana use, suggesting that intervention strategies may be more effective if they are targeted towards high use groups.

Blows, S., Ivers, R.Q., Connor, J., Ameratunga, S., Woodward, M., & Norton, R. (2005). Marijuana use and car crash injuryAddiction, 100(5), 605-611.


Acute cannabis consumption and motor vehicle collision risk: Systematic review of observational studies and meta-analysis

Objective To determine whether the acute consumption of cannabis (cannabinoids) by drivers increases the risk of a motor vehicle collision. Design. Systematic review of observational studies, with meta-analysis. Data sources. We did electronic searches in 19 databases, unrestricted by year or language of publication. We also did manual searches of reference lists, conducted a search for unpublished studies, and reviewed the personal libraries of the research team. Review methods. We included observational epidemiology studies of motor vehicle collisions with an appropriate control group, and selected studies that measured recent cannabis use in drivers by toxicological analysis of whole blood or self report. We excluded experimental or simulator studies. Two independent reviewers assessed risk of bias in each selected study, with consensus, using the Newcastle-Ottawa scale. Risk estimates were combined using random effects models. Results. We selected nine studies in the review and meta-analysis. Driving under the influence of cannabis was associated with a significantly increased risk of motor vehicle collisions compared with unimpaired driving (odds ratio 1.92 (95% confidence interval 1.35 to 2.73); P=0.0003); we noted heterogeneity among the individual study effects (I2=81). Collision risk estimates were higher in case-control studies (2.79 (1.23 to 6.33); P=0.01) and studies of fatal collisions (2.10 (1.31 to 3.36); P=0.002) than in culpability studies (1.65 (1.11 to 2.46); P=0.07) and studies of non-fatal collisions (1.74 (0.88 to 3.46); P=0.11). Conclusions. Acute cannabis consumption is associated with an increased risk of a motor vehicle crash, especially for fatal collisions. This information could be used as the basis for campaigns against drug impaired driving, developing regional or national policies to control acute drug use while driving, and raising public awareness.

Ashbridge, M., Hayden, J. A., & Cartwright, J. L. (2012). Acute cannabis consumption and motor vehicle collision risk: Systematic review of observational studies and meta-analysisBritish Medical Journal, 344.


Marijuana use and motor vehicle crashes

Since 1996, 16 states and the District of Columbia in the United States have enacted legislation to decriminalize marijuana for medical use. Although marijuana is the most commonly detected nonalcohol drug in drivers, its role in crash causation remains unsettled. To assess the association between marijuana use and crash risk, the authors performed a meta-analysis of 9 epidemiologic studies published in English in the past 2 decades identified through a systematic search of bibliographic databases. Estimated odds ratios relating marijuana use to crash risk reported in these studies ranged from 0.85 to 7.16. Pooled analysis based on the random-effects model yielded a summary odds ratio of 2.66 (95% confidence interval: 2.07, 3.41). Analysis of individual studies indicated that the heightened risk of crash involvement associated with marijuana use persisted after adjustment for confounding variables and that the risk of crash involvement increased in a dose-response fashion with the concentration of 11-nor-9-carboxy-delta-9-tetrahydrocannabinol detected in the urine and the frequency of self-reported marijuana use. The results of this meta-analysis suggest that marijuana use by drivers is associated with a significantly increased risk of being involved in motor vehicle crashes.

Li, M.-C., Brady, J. E., DiMaggio, C. J., Lusardi, A. R., Tzong, K. Y., & Li, G. (2012). Marijuana use and motor vehicle crashesEpidemiologic Reviews34(1), 65–72. 


Other Marijuana Research

National Institute on Drug Abuse. (2011). Marijuana: Facts Parents Need to Know. Washington, DC: National Institute on Drug Abuse.


National Institute on Drug Abuse. (2008, March). Marijuana: Facts for Teens. NIH Publication No. 08-4037.


National Institute on Drug Abuse. (2010). Marijuana Abuse. NIDA Research Report Series, NIH Publication Number 12-3859. US Department of Health and Human Services, National Institutes of Health.


The relationship between marijuana use and intimate partner violence in a nationally representative, longitudinal sample

Intimate partner violence is a significant public health problem, as these behaviors have been associated with a number of negative health outcomes including illicit drug use, physical injury, chronic pain, sexually transmitted diseases, depression, and posttraumatic stress disorder. The current study examined the association between marijuana use and intimate partner violence using a longitudinal survey of adolescents and young adults ages 15 to 26 years. Data were obtained from 9,421 adolescents in the National Longitudinal Study of Adolescent Health (Add Health) Waves 1 through 4 (1995-2008). Marijuana use was measured in the past year at each wave and participants were categorized as "users" or "nonusers." Partner violence was constructed using six items (three pertaining to victimization and three concerning perpetration) from Wave 4 (2007-2008). Using these six items, participants were categorized as "victims only," "perpetrators only," or "victims and perpetrators." Survey multinomial regression was used to examine the relationship between marijuana use and intimate partner violence. Consistent use of marijuana during adolescence was most predictive of intimate partner violence (OR = 2.08, p < .001). Consistent marijuana use (OR = 1.85, p < .05) was related to an increased risk of intimate partner violence perpetration. Adolescent marijuana use, particularly consistent use throughout adolescence, is associated with perpetration or both perpetration of and victimization by intimate partner violence in early adulthood. These findings have implications for intimate partner violence prevention efforts, as marijuana use should be considered as a target of early intimate partner violence intervention and treatment programming.

Reingle, J. M., Staras, S. A. S., Jennings, W. G., Branchini, J., & Maldonado-Molina, M. M. (2012). The relationship between marijuana use and intimate partner violence in a nationally representative, longitudinal sampleJournal of Interpersonal Violence, 27(8), 1562-1578.


Kouri, E. M. (2002, February 1). Does marijuana withdrawal syndrome exist Psychiatric Times, 19(2).


Development and Consequences of Cannabis Dependence

The past 10 to 15 years of clinical and basic research have produced strong evidence demonstrating that cannabis can and does produce dependence. Clinical and epidemiological studies indicate that cannabis dependence is a relatively common phenomenon associated with significant psychosocial impairment. Basic research has identified a neurobiological system specific to the actions of cannabinoids. Human and nonhuman studies have demonstrated a valid withdrawal syndrome that is relatively common among heavy marijuana users. Last, clinical trials evaluating treatments for cannabis dependence suggest that this disorder, like other substance dependence disorders, is responsive to intervention, yet the majority of patients have difficulty achieving and maintaining abstinence. Of concern, treatment seeking for marijuana dependence has increased almost twofold over the past 10 years. This report briefly reviews selected research literature relevant to our current understanding of cannabis dependence, its associated consequences, and treatment efficacy.

Budney, A. J., & Moore, B. A. (2002). Development and consequences of cannabis dependenceJournal of Clinical Pharmacology, 42, 28S-38S.


Alcohol

Beyond hangovers: understanding alcohol’s impact on your health

Alcohol is part of our culture—it helps us celebrate and socialize, and it enhances our religious ceremonies. But drinking too much—on a single occasion or over time—can have serious consequences for our health. Most Americans recognize that drinking too much can lead to accidents and dependence. But that’s only part of the story. In addition to these serious problems, alcohol abuse can damage organs, weaken the immune system, and contribute to cancers. Plus, much like smoking, alcohol affects different people differently. Genes, environment, and even diet can play a role in whether you develop an alcohol ­related disease. On the flip side,some people actually may benefit from drinking alcohol in small quantities. Sound complicated? It sure can be. To stay healthy, and to decide what role alcohol should play in your life, you need accurate, up-­to-­date information. This brochure from the National Institute on Alcohol Abuse and Alcoholism (NIAAA) is designed to offer you guidance based on the latest research on alcohol’s effect on your health


Underage binge drinking can create lasting brain changes

Experts agree that adolescence marks a critical period for brain development. New research from UNC School of Medicine shows that binge-drinking teens risk lasting brain changes that could affect their lives as adults. Summary.

Associated Article Abstract:

Background:  Binge drinking is common in human adolescents. The adolescent brain is undergoing structural maturation and has a unique sensitivity to alcohol neurotoxicity. Therefore, adolescent binge ethanol may have long-term effects on the adult brain that alter brain structure and behaviors that are relevant to alcohol-use disorders.

Methods:  To determine whether adolescent ethanol (AE) binge drinking alters the adult brain, male C57BL/6 mice were treated with either water or ethanol during adolescence (5 g/kg/d, i.g., postnatal days P28 to P37) and assessed during adulthood (P60 to P88). An array of neurotransmitter-specific genes, behavioral tests (i.e., reversal learning, prepulse inhibition, and open field), and postmortem brain structure using magnetic resonance imaging (MRI) and immunohistochemistry, were employed to assess persistent alterations in adult brain.

Results:  At P38, 24 hours after AE binge, many neurotransmitter genes, particularly cholinergic and dopaminergic, were reduced by ethanol treatment. Interestingly, dopamine receptor type 4 mRNA was reduced and confirmed using immunohistochemistry. Normal control maturation (P38 to P88) resulted in decreased neurotransmitter mRNA, e.g., an average decrease of 56%. Following AE treatment, adults showed greater gene expression reductions than controls, averaging 73%. Adult spatial learning assessed in the Morris water maze was not changed by AE treatment, but reversal learning experiments revealed deficits. Assessment of adult brain region volumes using MRI indicated that the olfactory bulb and basal forebrain were smaller in adults following AE. Immunohistochemical analyses found reduced basal forebrain area and fewer basal forebrain cholinergic neurons.

Conclusions:  Adolescent binge ethanol treatment reduces adult neurotransmitter gene expression, particularly cholinergic genes, reduces basal forebrain and olfactory bulb volumes, and causes a reduction in the density of basal forebrain acetylcholine neurons. Loss of cholinergic neurons and forebrain structure could underlie adult reversal learning deficits following adolescent binge drinking.

Coleman Jr, L. G., He, J., Lee, J., Styner, M., & Crews, F. T. (2011), Adolescent Binge Drinking Alters Adult Brain Neurotransmitter Gene Expression, Behavior, Brain Regional Volumes, and Neurochemistry in Mice. Alcoholism: Clinical and Experimental Research, 35, 671-688.


Arrhythmias and the “Holiday Heart”: Alcohol associated cardiac rhythm disorders

An association between excessive alcohol use and cardiac rhythm disorders is often difficult to establish in the absence of overt cardiomyopathy. We studied 32 separate hospital admissions for dysrhythmias in 24 patients (20 men, 4 women) with heavy recent alcohol ingestion and prolonged excessive alcohol use. None had evidence of overt heart disease after treatment of arrhythmia. Episodes usually followed heavy weekend or holiday sprees, resulting in hospitalization between Sunday and Tuesday or in proximity to the year-end holidays, a relationship not observed in other alcohol-associated illnesses. Atrial fibrillation was most common, but atrial flutter, atrial tachycardia, junctional tachycardia, multiple APC's, multiple PVC's and ventricular tachycardia were also observed. Transient hypokalemia was present in four of 30. The mean PEPLVET ratio after treatment was 0.412 ± 0.014 (normal 0.299 ± 0.008, P < 0.001). High-speed ECG's showed prolongation of PRc, QRS, and QTc. At cardiac catheterization, intracardiac pressures and volumes, coronary arteriograms and ventricular wall motion were normal at rest and mean cardiac index was slightly low, but the left ventricular response to angiotensin was abnormal. Cardiac arrhythmias presenting during weekend or holiday drinking episodes are associated with conduction delays and depressed cardiac performance indicative of early cardiomyopathy and suggest a “holiday heart” syndrome.

Ettinger, P., Wu, C., Cruz, C., Weisse, A., Sultan Ahmed, S., & Regan, T. (1978). Arrhythmias and the “Holiday Heart”: alcohol associated cardiac rhythm disordersAmerican Heart Journal, 95(5), 555-562.


Different measures of alcohol consumption and risk of coronary heart disease and all-cause mortality: 11-year follow-up of the Whitehall II Cohort Study

Aims: To investigate the relationship between three measures of alcohol consumption obtained simultaneously in a large cohort and the validated risk of coronary heart disease and all-cause mortality during follow-up.

Design: Prospective cohort study with median follow-up of 11 years.

Setting:The Whitehall II Cohort Study: London-based civil service.

Participants: A total of 10,308 (33% female) civil servants aged 35-55 years at baseline (1985-88).

Measurements: Self-reported volume of alcohol consumed during past week, frequency of drinking over past year, usual amount consumed per drinking session.

Main Outcome Measures: Coronary heart disease and all-cause mortality until 1999.

Findings: A U-shaped relationship was found between volume of alcohol consumed per week and outcome. Compared to those who drank moderately (10-80 g alcohol per week), non-drinkers and those drinking more than 248 g per week had approximately a twofold increased risk of mortality. The optimal frequency of drinking was between once or twice a week and daily, after adjustment for average volume consumed per week. Those drinking twice a day or more had an increased risk of mortality (male hazard ratio 2.44 95% CI 1.31-4.52) compared to those drinking once or twice a week. Drinking only once a month or only on special occasions had a 50% increased risk of mortality. The usual amount consumed per drinking session was not indicative of increased health risk in this cohort.

Conclusions: Epidemiological studies should collect information on frequency of drinking in addition to average volume consumed in order to inform sensible drinking advice.

Britton, A., & Marmot, M. (2004). Different measures of alcohol consumption and risk of coronary heart disease and all-cause mortality: 11-year follow-up of the Whitehall II Cohort StudyAddiction, 99(1), 109-116.


Alcohol Related Liver Disease

This guide from the American Liver Foundation explains the effects of alcohol on the liver and some of the possible consequences of alcohol use.


Tobacco

E-Cigarette Use Among Youth and Young Adults. A Report of the Surgeon General

Tobacco use among youth and young adults in any form, including e-cigarettes, is not safe. In recent years, e-cigarette use by youth and young adults has increased at an alarming rate. E-cigarettes are now the most commonly used tobacco product among youth in the United States. This timely report highlights the rapidly changing patterns of e-cigarette use among youth and young adults, assesses what we know about the health effects of using these products, and describes strategies that tobacco companies use to recruit our nation’s youth and young adults to try and continue using e-cigarettes. The report also outlines interventions that can be adopted to minimize the harm these products cause to our nation’s youth. E-cigarettes are tobacco products that deliver nicotine. Nicotine is a highly addictive substance, and many of today’s youth who are using e-cigarettes could become tomorrow’s cigarette smokers. Nicotine exposure can also harm brain development in ways that may affect the health and mental health of our kids. E-cigarette use among youth and young adults is associated with the use of other tobacco products, including conventional cigarettes. Because most tobacco use is established during adolescence, actions to prevent our nation’s young people from the potential of a lifetime of nicotine addiction are critical. E-cigarette companies appear to be using many of the advertising tactics the tobacco industry used to persuade a new generation of young people to use their products. Companies are promoting their products through television and radio advertisements that use celebrities, sexual content, and claims of independence to glamorize these addictive products and make them appealing to young people.

U.S. Department of Health and Human Services. (2016). E-Cigarette Use Among Youth and Young Adults. A Report of the Surgeon General. Atlanta, GA: DHHS.


Association of Electronic Cigarette Use With Initiation of Combustible Tobacco Product Smoking in Early Adolescence

Importance  Exposure to nicotine in electronic cigarettes (e-cigarettes) is becoming increasingly common among adolescents who report never having smoked combustible tobacco.

Objective  To evaluate whether e-cigarette use among 14-year-old adolescents who have never tried combustible tobacco is associated with risk of initiating use of 3 combustible tobacco products (ie, cigarettes, cigars, and hookah).

Design, Setting, and Participants  Longitudinal repeated assessment of a school-based cohort at baseline (fall 2013, 9th grade, mean age = 14.1 years) and at a 6-month follow-up (spring 2014, 9th grade) and a 12-month follow-up (fall 2014, 10th grade). Ten public high schools in Los Angeles, California, were recruited through convenience sampling. Participants were students who reported never using combustible tobacco at baseline and completed follow-up assessments at 6 or 12 months (N = 2530). At each time point, students completed self-report surveys during in-classroom data collections.

Exposure  Student self-report of whether he or she ever used e-cigarettes (yes or no) at baseline.

Main Outcomes and Measures  Six- and 12-month follow-up reports on use of any of the following tobacco products within the prior 6 months: (1) any combustible tobacco product (yes or no); (2) combustible cigarettes (yes or no), (3) cigars (yes or no); (4) hookah (yes or no); and (5) number of combustible tobacco products (range: 0-3).

Results  Past 6-month use of any combustible tobacco product was more frequent in baseline e-cigarette ever users (n = 222) than never users (n = 2308) at the 6-month follow-up (30.7% vs 8.1%, respectively; difference between groups in prevalence rates, 22.7% [95% CI, 16.4%-28.9%]) and at the 12-month follow-up (25.2% vs 9.3%, respectively; difference between groups, 15.9% [95% CI, 10.0%-21.8%]). Baseline e-cigarette use was associated with greater likelihood of use of any combustible tobacco product averaged across the 2 follow-up periods in the unadjusted analyses (odds ratio [OR], 4.27 [95% CI, 3.19-5.71]) and in the analyses adjusted for sociodemographic, environmental, and intrapersonal risk factors for smoking (OR, 2.73 [95% CI, 2.00-3.73]). Product-specific analyses showed that baseline e-cigarette use was positively associated with combustible cigarette (OR, 2.65 [95% CI, 1.73-4.05]), cigar (OR, 4.85 [95% CI, 3.38-6.96]), and hookah (OR, 3.25 [95% CI, 2.29-4.62]) use and with the number of different combustible products used (OR, 4.26 [95% CI, 3.16-5.74]) averaged across the 2 follow-up periods.

Conclusions and Relevance  Among high school students in Los Angeles, those who had ever used e-cigarettes at baseline compared with nonusers were more likely to report initiation of combustible tobacco use over the next year. Further research is needed to understand whether this association may be causal.

Leventhal, A. M., Strong, D. R., Kirkpatrick, M. G., Unger, J. B ., Sussman, S., Riggs, N. R., ..., & Audrain-McGovern, J. (2015). Association of electronic cigarette use with initiation of combustible tobacco product smoking in early adolescenceJAMA, 314(7), 700-707. 


The Health Consequences of Smoking: 50 Years of Progress. A Report of the Surgeon General

Over the past 50 years, 31 Surgeon General’s reports have utilized the best available evidence to expand our understanding of the health consequences of smoking and involuntary exposure to tobacco smoke. The conclusions from these reports have evolved from a few causal associations in 1964 to a robust body of evidence documenting the health consequences from both active smoking and exposure to secondhand smoke across a range of diseases and organ systems. The 2004 report concluded that smoking affects nearly every organ of the body, and the evidence in this report provides even more support for that finding. A half century after the release of the first report, we continue to add to the long list of diseases caused by tobacco use and exposure to tobacco smoke. This report finds that active smoking is now causally associated with age-related macular degeneration, diabetes, colorectal cancer, liver cancer, adverse health outcomes in cancer patients and survivors, tuberculosis, erectile dysfunction, orofacial clefts in infants, ectopic pregnancy, rheumatoid arthritis, inflammation, and impaired immune function. In addition, exposure to secondhand smoke has now been causally associated with an increased risk for stroke. Smoking remains the leading preventable cause of premature disease and death in the United States. The science contained in this and prior Surgeon General’s reports provide all the information we need to save future generations from the burden of premature disease caused by tobacco use. However, evidence-based interventions that encourage quitting and prevent youth smoking continue to be underutilized. This report strengthens our resolve to work together to accelerate and sustain what works—such as hard-hitting media campaigns, smoke-free air policies, optimal tobacco excise taxes, barrier-free cessation treatment, and comprehensive statewide tobacco control programs funded at CDC-recommended levels. At the same time, we will explore “end game” strategies that support the goal of eliminating tobacco smoking, including greater restrictions on sales

U.S. Department of Health and Human Services. (2014). The Health Consequences of Smoking: 50 Years of Progress. A Report of the Surgeon General. Atlanta, GA: DHHS.

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