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The Effects of Marijuana on the Teenage Brain

The Effects of Marijuana on the Teenage BrainMarijuana Use Among Teens

The Substance Abuse and Mental Health Agency reports that marijuana is the most commonly used illicit substance in the United States, according to results from the 2018 National Survey on Drug Use and Health. An estimated 43.5 million individuals reported using marijuana during the past year.1 Marijuana use is widespread among young people. Some statistics of its use include:1-2

  • 3.1 million adolescents aged 12 to 17 (about 1 in 8) used marijuana in the past year
  • 11.8 million young adults aged 18 to 25 (about 1 in 3) used marijuana in the past year
  • 14% of 8th graders have used marijuana in their lifetime
  • 33% of 10th graders have used marijuana in their lifetime
  • 44% of 12th graders have used marijuana in their lifetime
  • 22% of 12th graders have used marijuana in the past month
  • 6% of 12th graders (about 1 in 16) use marijuana on a daily basis

The Effect of Marijuana on the Teenage Brain

When a person uses marijuana, the principal psychoactive chemical called tetrahydrocannabinol (THC) passes from the lungs (with smoking) or digestive tract (with edibles) into the bloodstream. The blood carries THC to the brain, where it acts on specific cannabinoid receptors. These receptors are predominantly found in areas of the brain associated with concentration, thinking, sensory and time perception, pleasure, memory, and coordination.3 Overactivation of these areas by THC causes the “high” that people feel.4 Marijuana use can impair functions such as attention, memory, and learning, and these effects can last up to several days beyond the time of actual “high”.5

Unfortunately for teenagers, marijuana use can have much more long-term effects. The teenage brain is not yet fully mature, with neurodevelopment continuing until at least the early or mid-20s. During adolescence the brain is particularly sensitive to drug exposure, and marijuana use impacts how connections are formed within the brain.3 Other effects on the developing brain include interference with neurotransmitters and abnormal brain shape and structure volume.6

Studies have shown that the use of marijuana is associated with reduced cognitive function in teens.7 One study found that teens who regularly use marijuana lose an average of 5.8 IQ points by the time they reach adulthood.8 A recent study found that marijuana has a more negative impact on a teenager’s cognitive development than alcohol.9

Other long-term risks associated with marijuana use include respiratory issues, increased chance of lung cancer and heart attack, problems with child development during and after pregnancy, and the development of Cannabinoid Hyperemesis Syndrome (characterized by cycles of severe nausea, vomiting, and dehydration that may require emergency medical attention).10

Treatment Options

If you suspect your teen is suffering from marijuana abuse, you should seek professional help.

Treatment plans should be customized to address your teen’s unique abuse patterns and any related medical, psychiatric, and social problems. People with marijuana use disorders, especially adolescents, often also suffer from other mental health issues.11 It is most effective to approach such a dual diagnosis with an integrated intervention, which allows a person to be treated for both their mental illness and substance abuse at the same time.

Although outpatient treatment programs are convenient and will allow your teen to stay in school, some adolescents will benefit more from inpatient treatment. Treatment will likely include cognitive behavioral therapy, an important tool that identifies and changes your teen’s attitudes and behaviors related to substance abuse and other co-occurring problems.


  1. Substance Abuse and Mental Health Agency. (2019). Key Substance Use and Mental Health Indicators in the United States: Results from the 2018 National Survey on Drug Use and Health.
  2. National Institute on Drug Abuse. (2019). Monitoring the Future Study: Trends in Prevalence of Various Drugs.
  3. National institute on Drug Abuse. (2019). Marijuana.
  4. National institute on Drug Abuse. (2019). How does marijuana produce its effects?
  5. National institute on Drug Abuse. (2019). What are marijuana’s long-term effects on the brain?
  6. Squeglia, L.M., Jacobus, J., & Tapert, S.F. (2009). The influence of substance use on adolescent brain development. Clinical EEG and Neuroscience, 40(1), 31-8.
  7. Scott, J.C., Slomiak, S.T., Jones, J.D., Rosen, A.F., Moore, T.M., & Gur, R.C. (2018). Association of Cannabis With Cognitive Functioning in Adolescents and Young Adults: A Systematic Review and Meta-analysis. JAMA Psychiatry, 75(6), 585-595.
  8. Meier, M.H., Caspi, A., Ambler, A., Harrington, H., Houts, R., Keefe, R.S., …& Moffitt, T.E. (2012). Persistent cannabis users show neuropsychological decline from childhood to midlife. Proceedings of the National Academy of Sciences, 109(40), 2657-2664.
  9. Morin, J.G., Afzali , M.H., Bourque , J., Stewart , S.H., Séguin , J.R., O’Leary-Barrett , M., &. Conrod, P.J.. (2018). A Population-Based Analysis of the Relationship Between Substance Use and Adolescent Cognitive Development. The American Journal of Psychiatry, 176(2), 98-106.
  10. Galli, J.A., Sawaya, R.A., & Friedenberg, F.K. (2012). Cannabinoid Hyperemesis Syndrome. Current Drug Abuse Reviews, 4(4), 241-249.
  11. Diamond, G., Panichelli-Mindel, S.M., Shera, D., Dennis, M., Tims, F., & Ungemack, J. (2006). Psychiatric Syndromes in Adolescents with Marijuana Abuse and Dependency in Outpatient Treatment. Journal of Child & Adolescent Substance Abuse,15(4), 37-54.
Last Updated on December 23, 2019
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Michael Kaliszewski, PhD
Dr. Michael Kaliszewski is a freelance science writer with over 15 years of experience as a research scientist in both academia and industry.
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