A Canadian study has found that teenagers who use cannabis may suffer long-lasting damage to their developing brains, with effects on memory, reasoning, and behaviour worse than those caused by alcohol.
Researchers from the University of Montreal tracked 3,800 adolescents over four years, starting at around age 13. The teens provided annual reports on their drug and alcohol use and underwent computer-based cognitive tests. While 75% drank alcohol at least occasionally, 28% admitted to some cannabis use.
The study, published in the American Journal of Psychiatry, found that cognitive problems increased with cannabis use and persisted even after stopping, unlike alcohol-related effects. Impairments were noted in working memory, reasoning, and behavioural control.
Lead author Prof Patricia J Conrod said she had expected alcohol to have a greater impact, but cannabis use led to more errors in cognitive tests. 'Their brains are still developing but cannabis is interfering with that,' she said, urging teens to delay cannabis use as long as possible.
Cannabis is the most widely used illegal drug in the UK and is known to increase the risk of psychotic illnesses, especially in adolescents. Withdrawal can cause sleep problems and mood swings.
