The Effects of Marijuana on the Teenage Brain

Posted February 13th, 2013 in Anxiety, Christian Counseling for Children, Christian Counseling For Teens, Family Counseling by

The aim of this article is to share some of the recent research examining the impact of marijuana on the developing teenage brain. In 2012, eleven percent of 8th graders, twenty-eight percent of 10th graders, and thirty-six percent of 12th graders reported using marijuana at least once in the past year1. Studies have also shown that in the past few years the amount of risk that teens perceive in using marijuana has dropped1. Given these findings it is important for teens and parents to be aware of what research is telling us concerning the risks associated with teenage marijuana use.

human_brainThe Developing Brain:

In recent years, advancements in technology have allowed researchers to more fully examine the process of human brain development. Today, researchers believe the brain does not reach full development until a person is in their early 20s. The implication of this finding is that teenage brains are still involved in an incredibly intricate process of change. Some of these changes occur in the outer most layer of the brain, called the cortex, which is involved in activities such as complex thought processes, impulse control, and planning2. The emotional circuitry of the teen brain is also still under development in adolescent years, and appears to be more active in teens than in either children or adults2. Needless to say, the changes that occur in the brain during adolescence have significant implications for a person’s long-term mental health.

How Marijuana Acts on the Brain:

The primary active ingredient in marijuana is the chemical Delta-9-tetrahydrocannabinol or THC. When marijuana is smoked (or consumed), THC makes its way into the bloodstream, and then into the brain. Like nearly all drugs of abuse, THC produces its effects by activating dopamine receptors that play an important role in the brain’s reward system. Specifically, THC attaches to the cannabinoid receptors in the brain, which are particularly abundant in areas related to pleasure, judgment, memory, learning, movement, and more3. Overtime, as THC repeatedly over-stimulates these receptors their functioning can be altered and symptoms of addiction and withdrawal may develop.

What is the Research Telling Us?

In a recent 20-year study involving 1,037 participants, researchers examined the relationship between marijuana use and neuropsychological health4. They found that long-term use was associated with broad neuropsychological decline, revealed primarily as a drop in IQ score. This decline was especially apparent for those who started using marijuana before age 18. These findings are consistent with the results of similar studies suggesting impairments in executive functioning, verbal IQ, learning, and memory in adolescent-onset marijuana users4. One of these studies, published in Psychology of Addictive Behaviors in 2011, found that earlier onset of marijuana use (before age 16) was associated with poorer cognitive functioning, higher frequency of use, and higher amounts of use compared to later-onset users5. As a result of the combined results of these and similar studies, it appears that marijuana may have a toxic effect that is particularly pronounced in the still-developing brain of adolescents4. According to Dr. Nora Volkow, director of the National Institute on Drug Abuse, “the message inherent in these and multiple supporting studies is clear. Regular marijuana use in adolescence is known to be part of a cluster of behaviors that can produce enduring detrimental effects and alter the trajectory of a young person’s life” (NIDA).

smokerWhat Do I Do if My Teen is Using?

 If you’re the parent of a teen who is using marijuana, the best place to start is by having an open conversation about drug use with your teen. This is not always an easy conversation to have, so it may help to start by solidifying your own understanding of marijuana and it’s particular risks for teen users. The National Institute on Drug Abuse is a good place to start for gathering information and reading tips for parents ( As you prepare for this conversation it may be helpful to consult with a professional counselor who is knowledgeable and experienced in this area. Whether you would like a counselor to facilitate a conversation between you and your teen, or you are simply looking for skills and support in this process, a trained counselor can help ease the way.

It is also important to recognize that teens use substances for a number of different reasons, including fitting in with peers, curiosity, and coping with depression, anxiety, struggles with school, or boredom. Encouraging your teen to talk with a licensed counselor may allow them to more completely and honestly explore their struggles and step into the recovery process. If you would like more information about counseling for teens and parents, please contact Seattle Christian Counseling or any one of our licensed counselors.


  1. Johnston, L. D., O’Malley, P. M., Bachman, J. G., & Schulenberg, J. E. (December 19, 2012). “The rise in teen marijuana use stalls, synthetic marijuana use levels, and use of ‘bath salts’ is very low.” University of Michigan News Service: Ann Arbor, MI. Retrieved 01/25/2013 from
  2. National Institute of Mental Health. (2011). The teen brain: Still under construction. Retrieved from
  3. National Institute on Drug Abuse. (2012). Marijuana abuse. Retrieved from
  4. Meier, M.H., Caspi, A., Ambler, A., Harrington, H., Houts, R., Keefe R.S.E.,…Moffit, T.E. (2012). Persistent cannabis users show neuropsychological decline from childhood to midlife. Proceedings of the National Academy of Sciences, 109(40). Retrieved from
  5. 5. Gruber S.A., Sagar K.A., Dahlgren M.K., Racine M., Lukas S.E. (2011) Age of onset of 
marijuana use and executive function. Psychology of Addictive Behaviors, 26(3). doi: 10.1037/a0026269.
  6. Volkow, N. (January 2013). Marijuana’s lasting effect on the brain. In Messages from the director. Retrieved from


Images cc: -“Human Brain” by koratmember
“Smoking Addiction” by mack2happy


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