A study published in the American Journal of Psychiatry suggests that cannabis use may be more harmful to developing teenage brains than alcohol, BBC reports.
The study was conducted with 3,800 adolescent participants tracked over 4 years from just before high school until graduation. All participants were from the greater Montreal area in Quebec, Canada. Participants were tested once per year using computerized tests. The data was analyzed with statistical controls to isolate the effects of various substances used.
While both alcohol and cannabis showed negative effects on cognitive abilities, cannabis use at this stage of development had long-lasting effects that did not disappear once the teens stopped consuming cannabis. Researchers have shown in a number of other studies that teenage cannabis use can have permanent effects on cognition, learning ability and memory.
Researchers theorize that the brain development happening in teenage years may be largely controlled by the body’s own cannabinoids and that consumption of phytocannabinoids — which come from the cannabis plant — may permanently change how the brain develops into adulthood.
In contradiction, a meta-study of all research to date by the University of Pennsylvania showed that the research — which, in individual studies, seemed to find consistent impairment for teens — may have overstated the damage caused by cannabis use due to the studies’ designs, which did not account for withdrawal due to non-consumption while participating in a clinical study or even simply lingering traces in the body.
The lead author of the Montreal study, professor Patricia Conrod, said she had expected alcohol to have a more significant effect than cannabis and was surprised by the results.
“They should delay their use of cannabis as long as they can,” said Prof. Conrod.