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Cannabis Effect on the Brain

Cannabis’ Effect on the Brain

Recreational cannabis use in California is legal only for people age 21 and older, but many younger people use it as well. That raises questions about how marijuana affects adolescents, and parents are understandably concerned.

Teenagers are natural risk takers, and while we keep a close eye on them, we can’t follow them everywhere to keep them safe. But some risky activities can have lasting consequences, and parents are right to be concerned.

The marijuana products available today, are not the same potency of those developed in years past. According to Dan Becker, MD., medical director of Scrivner Center for Mental Health and Addiction Services at El Camino Health, “During the past three decades, the potency of marijuana has approximately tripled. This change has greatly increased the health risks associated with using it, as well as the potential of becoming addicted.”


The Developing Brain

Teens are a particularly vulnerable population with respect to the effects of marijuana on the brain. Up until the mid 20’s the brain is still undergoing important development including areas that control judgement and decision making. There is evidence that chronic marijuana use during this period is linked to a decline in IQ as detailed by the National Institute on Drug Abuse. And the deficits don’t improve over time.

Marijuana and Thinking Skills

Marijuana impairs concentration, memory and problem solving skills. Not surprisingly, these are critical skills youth employ while in school and in a learning environment. According to the CDC, frequent use by adolescents in this age group is linked to a higher likelihood of school dropout compared with peers who do not use.

Cannabis and Driving

The idea that people are safe drivers when they use marijuana is a myth. THC (the psychoactive component of marijuana) impairs judgement, coordination, and reaction time according to the article Does marijuana use affect driving? at National Institute on Drug Abuse.

Even if your teen doesn’t have an accident while driving, testing positive for marijuana while driving can cost them their driver’s license. According to the California Driver Handbook, drivers under the age of 21 driving under the influence of drugs will have their driving privilege revoked for one year, and on the first offense be required to complete the educational portion of a licensed DUI program.

Marijuana and Addiction

Legalization of marijuana can influence the impression that the substance is not harmful or potentially risky. According to data from the article Marijuana Addictive at National Institute on Drug Abuse adolescents who use marijuana are four to seven times more likely to develop a marijuana use disorder compared to the likelihood of developing the same disorder as an adult. Dr. Becker states, “It isn’t a myth that marijuana use precedes the use of other drugs. Research has documented that marijuana use in adolescence can influence addictive behaviors later in life.”

Talking With Your Teen

Now that marijuana use is legal in many states, including California, teens often perceive it as less risky or even safe. With increased exposure to it in the media, advertisements, and through storefronts in our community, parents can begin conversations with their teens.

It can be difficult to start these conversations but the simplest way is to listen. Take something as simple as a car ride as a chance to start a dialogue with your teenager and ask open-ended questions about their day, friends or school. Be curious about what your teens are doing, in a nonjudgmental way. Ask your child what they know or have heard about marijuana and offer facts about the risks and consequences to help shape ideas and discussion. Help them think out loud about how it might affect them personally. Good communication is key to opening the door to ongoing conversation about this topic. Need some additional support? The Partnership for Drug-Free Kids offers a free guide to discussing marijuana with teens. The Marijuana Talk Kit includes facts on marijuana and its effects on teen brain development, common questions posed by teens and suggested responses, along with tips on keeping the conversation productive. Download a copy.

If you or a loved one is showing signs of substance use, depression, anxiety or another mental health condition, the first step is to schedule a free, confidential assessment. Call El Camino Health’s Scrivner Center for Mental Health & Addiction Services at 866-789-6089. Our Mental Health Resource Coordinator is also available for those who just want to learn more and get connected to additional resources in the community.

This information was presented by Dr. Daniel Becker, chief medical director of the Scrivner Center for Mental Health & Addiction Services, at the Cannabis and the Adolescent Brain community lecture.


This article first appeared in the July/August 2019 edition of the HealthPerks newsletter and was updated in August 2023.