First Person Perspective

Cannabis and the Adolescent Brain: High Time for Mental Illness


A recently published study showed that from 2006 to 2014, the perception by teens that using cannabis has no risk increased from 5% to 12.8%. With 10 states having already legalized cannabis, the legalization and medicalization of cannabis has led the public to think of it as just another drug, like alcohol and tobacco.

Policy makers have focused on adults and the monetary gains that come from legalization; the effects on vulnerable teens have been an afterthought. Yet we know that cannabis affects brain development and increases the risk for mental health disorders.

The active chemical ingredient in cannabis, Tetrahydrocannabinol (THC), interferes with brain development, impacting the areas that help the brain work more efficiently. These brain areas selectively impacted by THC are the ones responsible for helping teenagers develop lifelong habits and routines. 

Some studies have estimated that chronic cannabis use during teenage years can lead to mild cognitive impairment later, which can translate to a drop in IQ points. While some children may only be impacted slightly, for others, this cognitive impairment can become the difference between passing and failing. And while this is the effect of chronic use, even short-term use causes memory impairment, which can impact school performance. Within my practice, I have seen an increase in the number of adolescents who struggle with cannabis use disorder, which affects their academics and personal life.

Potentially more problematic for teens is the increased risk for those who have a genetic predisposition to developing a mental health condition. What this ultimately means is that if your child inherits genes thought to be related to psychiatric illness, cannabis use can increase the likelihood that those genes will be expressed.

Cannabis also has a higher addiction potential for those who begin using it in adolescence, especially daily users. While 9% of adults who use cannabis become addicted, 17% of those who start in adolescence, including 25 to 50% of those who use it daily, will become addicted. The symptoms of cannabis addiction can include sleeplessness, irritability, paranoia, and aggression, which sometimes results in psychiatric hospitalization or needing substance abuse treatment.   

If you suspect your teen is using cannabis, Sheppard Pratt Health System is here to help. Learn about the comprehensive substance use and mental health services we offer throughout Maryland at

Dr. Villani is the medical director of the Berkley and Eleanor Mann Residential Treatment Program at Sheppard Pratt Health System.