New study shows alcohol and marijuana damages teens mental abilities

alcohol and drugs
Drinking during adolescence may have detrimental effects on mental and physical health. Source: iStock

A new study performed by a research team led by Dr. Elizabeth D’Amico found that using weed and alcohol during adolescence may reduce one’s mental faculties. The behavioral expert and her colleagues examined 6,509 high and middle students from Southern California, half of which used these substances. All the boys and girls had to complete a total of seven surveys to check their academic outcomes as well as their mental health. The students were between 11 and 17 years of age and were examined by scientists from the RAND Corporation, a non-profit organization. They all participated in an alcohol and drug prevention program named CHOICE and came from 16 different schools across California. The questionnaire included questions about all types of topics such as physical and mental health, social performance, academic results, and past criminal behaviors.

The results left no space for doubts. All the youths who used alcohol and marijuana during the course of their academic year had an increased chance of showing delinquent behaviors as well as much poorer academic results. But an even more concerning evidence was found that their brain development was negatively affected by the substances, as the students showed a poorer mental health. Curiously, though, even though adolescents of white ethnicity were those who used alcohol and marijuana more than the others, Hispanic and Black ones showed an even worse academic performance. Youths of Asian or multi-ethnic heritage, on the other hand, were those with the worst physical health.

In 2015, a different study indicated that marijuana’s effects on adolescents overall health are 114 times less dangerous. Still, as Dr. D’Amico explained, weed’s ability to negatively affect brain development and performance during adulthood is still poorly understood. While alcohol may eventually lead to serious brain damage with long-term use, there’s a significant chance that using marijuana during adolescence may have detrimental effects in a much shorter timeframe. Nonetheless, many youths perceive using these substances as a “cool thing” to do. According to recent statistics from the National Institute on Alcohol Abuse and Alcoholism, the average age of first alcohol use dropped from 17 years to 14 in the last four decades. The risk of becoming an alcoholic during adulthood is significantly increased in young subjects who start drinking before 15 years of age. Underage drinking is a contributing factor in several criminal behaviors such as sexual assaults and may have other life-threatening consequences since it increases the risk of serious injuries, car crashes, and even death.

Article written by Dr. Claudio Butticè, PharmD.



  1. Alcohol and marijuana use trajectories in a diverse longitudinal sample of adolescents: examining use patterns from age 11 to 17 years, Elizabeth D’Amico et al., Addiction, doi: 10.1111/add.13442, published online 14 June 2016,
  2. National Institute on Alcohol Abuse and Alcoholism (NIH). Underage Drinking. Accessed June 2016