Late use of cannabis limits its effect on the adolescent brain

According to a Canadian study, the risk of cognitive impairment is significantly reduced if moderate cannabis use begins after age 17. In contrast, early use (at ages 13 or 14) is associated with several types of cognitive decline.

A study conducted by researchers at the St. Justine University Hospital in Montreal has highlighted the correlations between early cannabis use during adolescence and its effects on cognitive function. According to this study, published in the Cambridge University Press, the risk of cognitive impairment is reduced if consumption begins after 17 years.

No final judgment

Thestudy was conducted on 294 young Canadian boys aged 13 to 20. They underwent cognitive tests (memorizing images, words, and numbers, and problem-solving) every year. The study defines cognitive impairments as anything related to verbal IQ and learning through trial and error. Adolescents who begin using cannabis at age 14 perform worse than those who start later. According to Natalie Castellanos Ryan, a co-author of the study: «Overall, these results indicate that, in addition to academic failure or shorter educational trajectories, the fundamental skills needed for problem-solving and adapting to daily life may be impaired by early exposure to cannabis. » However, she clearly states that cognitive declines are not neither widespread nor common and that the frequency of consumption can play a key role.

Are the Risks Over by Age 17?

The impairments are no longer noticeable once the adolescent reaches age 17: «We found that adolescents who began using cannabis at age 17 scored the same results »than those who had not smoked cannabis." However, the study’s author points out that the decline in verbal intelligence is not due to the active ingredients in cannabis but rather to the social changes that results from early use.

«However, it is important to stick to the evidence we have and not to exaggerate the harmful effects of cannabis. We cannot tell children, “If you smoke cannabis, you will greatly damage your brain ”and ruin your life.« She continues: »On the other hand, if you wait to try it until at least age 17, there will be less risk that it will affect your brain.".

At the same time, the author explains in this video YouTube that a person who starts using cannabis at an early age, engages in delinquent behavior, and uses other drugs is more likely to become a problem user in the future.  According to her, parental absence and living conditions during childhood, as well as genetic factors, could be linked to future addiction problems.

Natalie Castellanos-Ryan is a professor of psychoeducation at the University of Montreal and has conducted similar studies on early alcohol use.

Théo Caillart