How teen marijuana use impacts brain development

December 18, 2018

Marijuana is the most common illicit drug among adolescents and young adults, and surveys show fewer of this population now believe marijuana can cause harm. This decline in the perceived risk could lead to increased use of marijuana in future. It is important to know that research also shows marijuana use adversely impacts brain development in adolescents and young adults. Marijuana contains more than 500 chemicals, of which delta-9-tetrahydrocannabinol (THC) is considered to be the main psychoactive (mind-altering). The concentration of TCH in a marijuana product is directly proportional to its potency or how much of a high that product will give when consumed.

Key findings in a national survey on drug use reported daily use of marijuana as early as eighth grade and among 5.9 percent of high school seniors. In addition, 80 percent of seniors said that marijuana would be easy to get. These numbers are cause for concern.


The adolescent or teen brain continues to mature and develop until around age 25, especially in areas of the brain involved in planning, decision-making and learning, which develop last. This time window is considered a window of vulnerability where any disruption has abnormal and unwanted consequences. Research studies have shown that when marijuana is consumed, TCH and other compounds enter the bloodstream, reach the brain and attach to naturally occurring receptors called cannabinoid receptors. This causes problems in learning and memory, coordination, reaction time and judgment. It also can cause hallucinations, paranoia and a range of emotional problems. Marijuana use may cause academic difficulties, poor sports performance, impaired driving and troubled relationships.

Not every teen or young adult who uses marijuana becomes addicted because every person reacts differently. The effects of marijuana on an individual depend on the concentration of TCH in the marijuana product used, family history of addiction and person’s genetic susceptibility to addiction, addiction to other drugs and alcohol, environment and history of psychiatric illness. The severe form of marijuana abuse is called marijuana use disorder. Those who start using marijuana at an early age, in high amounts and with risk factors mentioned above, are more prone to developing marijuana use disorder.


Talking early with your child about the risks of marijuana use and continuing this discussion over time may prevent the first use and protect your child’s brain. If you suspect your child is using marijuana, have an open dialogue without making negative or angry comments. Offer your child educational material and facts about marijuana and its use. Involve your primary care physician or pediatrician to educate your child and screen for marijuana use so an appropriate referral for addiction treatment can be made.

Additional information is available from the Centers for Disease Control and the

National Institute on Drug Abuse.

Pravesh Sharma, M.D., Psychiatrist Behavioral Health at Mayo Health System in Eau Claire