Health Effects of Substance Use

Substance use poses serious negative health consequences for all age groups. The developing brains of kids are particularly vulnerable to the damaging effects of alcohol and other drug use, which can lead to life-long problems.


The Teen Brain

Beginning in the early teenage years and extending to the mid-twenties, the human brain undergoes a period of great change. During this period many teens tend to take more risks, seek high pleasure activities, and exhibit poor judgement. These facts make teenagers at heightened risk for drug use.

Adolescent brains are more vulnerable to damage by outside influences including drug use. Teens who use drugs are more likely to develop addiction, have difficulty making decisions, and experience less pleasure. These effects continue even after a person has stopped drug use. It is especially important for teens to protect their brains at this vulnerable time. 

Visit to take a 15-minute course for parents from the Center for Adolescent Substance Abuse Research (CeASAR) at Children’s Hospital Boston that explains the effects of alcohol and drugs on the developing teen brain, and gives science-based strategies for protecting adolescents from substance use.

Cognitive Impairment

Drug use is linked to short- and long-term cognitive impairment. Drug use can inhibit brain functions and can even alter the structure of developing brains. While effects vary by drug, there are some universal effects of drug use:

  • People who use drugs exhibit poor cognitive performance including, deficits in memory, difficulty learning and processing information. They also make more errors performing everyday tasks and have lower IQs. These deficits make performing everyday tasks much more difficult and limit academic success.

  • Behavior is also affected by this cognitive impairment. Drug users have lower inhibition and greater impulsivity. Considering adolescents are already prone to high impulsivity and risk taking, using drugs can exacerbate these traits.

  • These effects last well beyond adolescence. Even if teens only use drugs for a short period of time, the effects of this substance use on their brains, including cognitive deficits, can last well into adulthood. The younger a person starts using and the heavier the use, the greater the effects of that substance use on their brains.

Mental Health

People of all ages jeopardize their mental health when they use drugs. For people already experiencing or at risk for mental illness, drug use poses a greater threat to mental health. Several studies show that the effects of drug use can be life-long, even after a person stops using drug.

  • The 2014 National Survey on Drug Use and Health found that approximately 7.9 million adults in the US were suffering from substance use disorder as well as another mental disorder. This phenomenon is called comorbidity because the substance use disorder exists along with a mental health disorder. This happens because mental disorders put people at a higher risk for initiating drug use, and drug use can also trigger a mental health disorder among people at high risk. Substance use can also worsen symptoms of existing mental illnesses. Many drugs have been linked to depression, bipolar disorder, and personality disorders.

  • Substance use can also cause mental illnesses. For example, marijuana use can trigger psychosis. Substance users may experience hallucinations, depression, anxiety, and amnesia, among other symptoms even in the absence of a mental health disorder, especially during intoxication and withdrawal. While most symptoms of substance induced disorders typically end after a period of sustained abstinence, some symptoms last much longer.

  • The damage to mental health caused by substance use can last a lifetime. Long-term, heavy use of drugs like alcohol and inhalants cause damage to the brain often resulting in persistent symptoms of dementia and amnesia. Frequent tobacco and cannabis use lead to long-lasting depression and anxiety. For teens, there is a greater risk of long-term damage to the brain including mental health disorders.

Future Addiction

While all teens that use drugs do not become addicted, any drug use increases the chances of future addiction. People addicted to so-called “hard” drugs (opioids, cocaine, etc.) commonly began their drug use with alcohol, tobacco (nicotine) or marijuana, usually during their teen years. Avoiding any drug use until at least the age of 21 can reduce future addiction.

  • Drugs affect the brain reward system, making it difficult to experience pleasure naturally. The brain reward system creates feelings of pleasure when we are affected by certain outside stimuli such as running, hearing a joke, or eating. This pleasure makes people seek out the stimuli that caused that pleasure.

  • Drugs create pleasure that is far more intense than everyday healthy activities. This means that regular activities that would cause brain reward instead seem dull and not stimulating to regular drug users. Once the reward system has been altered, users commonly seek more drugs to experience that high again. The body, however, develops a tolerance to drugs, reducing the amount of reward a dose of the drug gives after repeated drug use. People then use more and more of that drug and begin to combine drugs in order to achieve a greater high. This drug abuse often leads to long-term addiction.

  • Nearly every drug user, including those with severe substance use disorders, started by using alcohol, tobacco (nicotine), or marijuana, or often all three. They also often started using drugs in their teen years. These drugs are commonly used because they are often accessible, falsely believed to be low risk, and use is believed by many youth to be normal.

  • Teens need to know that these drugs pose a serious threat to their health and should be avoided and that an increasingly large percentage of youth are making the decision not to use any alcohol, tobacco, marijuana or other drugs.


The average potency of today's marijuana is about 250% higher -- yes, you read that right -- than the average potency of marijuana smoked in the 1980s. As a result, today's marijuana is more addictive and harmful -- especially for adolescents, who are in crucial stages of brain development. Parents shouldn't dismiss today's teen marijuana use based on their own use of lower potency pot when they were young. What kids smoke today is not their parents' marijuana.

Largely because of the legalization of marijuana for medical and recreational use in several states, the drug is more available, accessible -- and socially accepted. Even though youth rates of drug use are generally down in the US, those same declines are not seen in rates of youth marijuana use. Data from the Monitoring the Future survey show that 22% of American high school seniors used marijuana in the past month and 6% used daily in 2016. Use rates have changed among young adults as well. Daily marijuana use by college students reached a 30-year record high and surpassed daily cigarette use for the first time in 2014. 

The combination of a stronger drug and more use is bad news. Decades of research on the negative effects of marijuana on the developing brain are yielding disturbing results. These findings -- many of which point to long-term and permanent cognitive deficits -- should concern parents and teenagers. Marijuana use is associated with:

  • lower academic achievement

  • high school and college dropout

  • serious mental health problems, and

  • chronic, lifelong struggle with drug addiction.

While many teenagers use marijuana with no apparent ill effects, the drug robs many others of their future.


Vaporizing is the intake of marijuana vapor by using a device that creates steam to inhale rather than the traditional inhalation of smoke produced by burning leaves. Vaping devices were originally developed to create an alternative way to inhale nicotine. The marijuana industry has co-opted these devices, which deliver a high percentage of THC rapidly to the bloodstream. For more about this topic check out "Vaping" - The Transformation of Marijuana.


Nora Volkow, MD, Director of the National Institute on Drug Abuse, presented on the effects of marijuana use on the brain, body and behavior at the 2014 CADCA National Leadership Forum. With regard to the changing legal status of marijuana through ballot initiatives, Dr. Volkow states that "people are voting without the knowledge."  Moreover, she notes that the reason alcohol and tobacco are the most widely used drugs is their legal status.


This brief documentary provides an inside look at weed culture at an unnamed high school in Portland, Oregon. Students share their experiences about smoking marijuana, including use of mooks, dabs, and other marijuana-based products. The documentary shows how marijuana use can lead to problems for many young people and demonstrates a disconnect that exists between students and teachers on the subject of drugs.


When we talk to teens about moderation, we are simply not speaking the same language. To many teens, six or seven drinks is moderation. The take-away message: Be clear when talking about alcohol and set a “no-use” policy as part of your house rules.
— Sharon Levy, MD, MPH. Director of Adolescent Substance Abuse Program at Boston Children's Hospital

Alcohol is one of the most commonly used drugs in the world. Some people believe that “moderate” drinking is harmless for teens. In reality, all teens that drink alcohol expose themselves to a greater risk for several health problems including problems in the brain, heart and liver. Fortunately, teen drinking has declined over the two decades and can continue to drop if teens know the risks of alcohol use.

  • Teens who consume alcohol often binge drink. This means consuming 5 or more drinks at one time. Consuming large amounts of alcohol at once can have severe impacts on the brain, even without continued alcohol use in the future.

  • While intoxicated, the brain’s communication pathways are impaired which disrupts mood and behavior and makes it difficult to think clearly.

  • Heavy drinking can lead to liver disease, one of the leading causes of death in the US.

  • Long term heavy drinking and binge drinking weakens the heart muscle, making it difficult to pump blood to the body’s organs, and can make the heart beat irregularly. Binge drinkers are also 39% more likely to suffer a stroke than those that never binge drink and may suffer from high blood pressure.


Tobacco use is the leading preventable cause of disease, disability and death in the United States. About 7 in 10 middle and high school students are exposed to e-cigarette adds online, in stores, and other media sources. Many teens begin using cigarettes or e-cigarettes under the impression that “experimenting” is harmless. No amount of tobacco use is safe. No form of tobacco is safe.

Smoking: Robbing the Future

Cigarette companies have a long history of marketing to youth. This video from the Centers for Disease Control and Prevention (CDC) explores the various ways the tobacco industry targets young people, the growing popularity of emerging products, such as e-cigarettes, and the dangers associated with those products. If we don't do more to prevent youth from starting to smoke, one out of every 13 children alive today in this country will die early from smoking.


Smoking is the leading preventable cause of death in the US. An ad campaign from the Centers for Disease Control and Prevention (CDC) features individuals who have stomas as a result of their smoking. They offer tips on how to live with this condition.

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