Cannabis causes long-term damage to teenagers’ brains, more harmful than alcohol, study finds

Canadian scientists have found that cannabis use causes long-term damage to the developing brains of teenagers and causes more damage than alcohol.

We often get conflicting information about this drug but this latest study involved almost 4,000 teens who were tracked between the ages of 13 and 17.

The study also found that cannabis reduces the mental capacity of teens to control the impulses associated with addictive behavior and can lead to heavier drug use.


As well as the intoxicating effects of cannabis and alcohol, their misuse has been associated with impairments in learning, memory, attention and decision-making, as well as with lower academic performance. The researchers, from the University of Montreal, say teens should delay their use, saying it affects “important cognitive functions.”

Advice from the Centre for Addictions Research of BC, in partnership with mental health associations for children, says all drug use carries some risk but  “generally, it is safest not to use any drug unless one can be sure the benefits clearly outweigh the risks and the context and reasons for use do not increase the potential for harm.”

Dr. Patricia Conrod, from the Department of Psychiatry at Université de Montréal, said,  “Our study is unique in that it followed a large sample of high school students from 7th to 10th grade using cognitive and substance-use measures.

“Using this big-data approach, we were able to model the complex nature of the relationship between these sets of variables.”

Researchers looked at year-to-year changes in substance use and cognitive development in recall memory, perceptual reasoning, inhibition, and working memory.

The study, published in the American Journal of Psychiatry, found that cannabis and alcohol use in adolescence was associated with generally lower performance on all the above areas.

“However, further increases in cannabis use, but not alcohol consumption, showed additional concurrent and lagged effects on cognitive functions, such as perceptual reasoning, memory recall, working memory and inhibitory control,” said Dr. Conrod

“Of particular concern was the finding that cannabis use was associated with lasting effects on a measure of inhibitory control, which is a risk factor for other addictive behaviors, and might explain why early onset cannabis use is a risk factor for other addictions.”

Find out more about this discovery in the video below and make sure you share this with all the parents and teenagers you know.