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Think. Discuss. Act. Marijuana

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Review: Brain Changes in Young Marijuana Users

Kay Lazar. “Study Finds Brain Changes in Young Marijuana Users.” The Boston Globe, 15 April 2014.


Marijuana has been popular in the news over the course of the last two or three years, specifically in relation to the legalization of medicinal marijuana. With Colorado and Washington State both voting in 2012 to have recreational use legalized, the topic among researchers has been what the effects of marijuana are on the brain, especially in young adults and adolescents. Kay Lazar, a reporter for the Boston Globe, struck the news headlines recently with a study showing the effect of marijuana on young adult brains during the formative years.  This study is especially pertinent because it could have a large impact on recreational and medicinal marijuana legalization in the future for states who have yet to approve those measures.

The study was done by Boston area researchers and shows that smoking marijuana casually as a young adult affects two parts of the brain. Those two key areas of their brain are the parts that are in control of emotion, motivation, and decision making. There has been other research done that has found heavy smoking of marijuana to alter the brain in some way, but this is the first that has found changes when the person is just a casual smoker. For growing adolescents at the age of self-discovery and self-determination, marijuana could be a dangerous drug if it does in fact have an effect on various parts of the brain.

Jodi Gilman, the lead author on this research study and a psychology instructor at Harvard Medical School as well as a brain scientist at Massachusetts General Hospital, says that these results are particularly worrisome: “This is when you are making major decisions in your life, when you are choosing a major, starting a career, making long-lasting friendships and relationships.”

This study was conducted in Boston and comprised 40 young adults from the area aged 18-25. The group was divided in half between those who use marijuana at least once a week and those who have not used marijuana in the last year and have reported using it less than five times in their life. The two parts of the brain that the researchers studied were the nucleus accumbens and the amygdala. The nucleus accumbens is vital to a person’s decision making and motivation. The amygdala is primarily involved with the emotions of a person.  In the scans, researchers measured the volume, shape and density of those two areas.

The scans showed some changes in the structure of the brain. The nucleus accumbens was larger in those that had used marijuana as opposed to those who had not. The alteration was directly related to how much a person had smoked. In the amygdale, structural changes were found as well. Gilman said that these changes could be that the brain is forming new connections which could perhaps encourage more drug use, as she termed it a “drug learning process.”

The opinion of some medical personnel has been that marijuana does have an altering effect on the brain in those who have smoked in their adolescence, but this study adds some substantial hard evidence to the case. This study shows that young adults are at risk for changes in their brain, even if they are casual smokers. One of the difficulties in many of these studies is that young adults often use other drugs in combination, making it difficult to get a good sense of which drug affects which part of the brain. There are so many unanswered questions about the long term effects of any of these drugs, but this study does provide some hard evidence that the brain of young adults is affected by even causal marijuana use.

Questions for Reflection and Discussion

  1. Do you think this study will have any political ramifications for states that are trying to legalize marijuana for medicinal or recreational use?
  2. How can we better educate our young adults about the possible lasting implications of casual marijuana use?
  3. Is there someone you know who is using marijuana as a young adult or adolescent? Have you noticed a change in their decision making or behavior?


Due to the popularity of the medical and recreational marijuana debate, this research provides lawmakers and citizens with concrete evidence as to what exactly goes on in the brain of a young adult who is a casual user. This study as well as others in the future will hopefully cause everyone to take a step back and reflect on the positive and negative effects of legalizing marijuana before critical decisions are made that could have life-altering effects for some people.

Joe Garrison
© 2018 CYS

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