Marijuana can even affect adolescents if they were passively exposed in utero. Adolescents passively exposed were found to have higher rates of depressive symptoms through age 21 years of age, as well as a higher risk of psychosis. In addition both of the longitudinal studies found these adolescents were at greater risk for substance abuse, especially marijuana and tobacco use.
Because of the developmental brain changes that occur during the teen years, the risks of marijuana use by adolescents are greater than those faced by adults. First, the risk of addiction is increased. 9% of all users become addicted, but 17% of those who begin use during their teen years do so.
Since the main active chemical in marijuana is THC that acts upon brain cells that have cannabinoid receptors, it is not surprising that marijuana will have specific effects on the areas of the brain with higher density of cannabinoid receptors – the hippocampus (involved in memory and learning) as well as the prefrontal cortex (involved in executive functions, decision making) and the amygdala (emotions).
A 2012 study of over 1000 people who were followed for over 25 years found that participants who used cannabis heavily in their teens and continued using through adulthood showed a significant drop in IQ of approximately 8 points between the ages of 13 and 38. However, those individuals who never used marijuana had no decline in IQ over the 25 years. Meier MH, Caspi A, Harrington H, et al. Persistent cannabis users show neuropsychological decline from childhood to midlife. 2012 Oct 2;109(40):E2657-64
Other studies have found that the damage to the hippocampus lasts after the drug use has ended, with verbal memory especially affected.
Especially significant is the increased risk of psychosis seen in those adolescents who use marijuana. “A review of 10 studies evaluating the possible link between cannabis use and the development of psychotic disorders found nearly a 50% increased risk of psychosis among cannabis users versus nonusers.” https://www.acpeds.org/marijuana-use-detrimental-to-youth
Initially researchers thought this increased risk was only found in individuals who had a positive family history of mental illness. However, more recent studies have found an increased risk for all adolescent users.
There are certainly other risks for adolescents, but worth noting is the contribution of marijuana to motor vehicle accidents, with marijuana being the most commonly detected non-alcohol drug identified in fatally injured drivers.
As you contemplate all the issues surrounding marijuana, please remember that parents do matter.
Teens are less likely to use alcohol and drugs if their parents express strong disapproval and are good role models themselves. In addition, remember that teens who are strongly connected to their families, participate in family meals, and contribute to their family by doing chores are much less likely to abuse drugs and alcohol.
For more information:
Hazards of Marijuana Use in...