Smoking cannabis could damage lining of smokers’ brains, research suggests amid fears over use of drug among teenagers

Teenagers who smoke cannabis may be damaging the lining of their brains, research shows.

Those who had smoked cannabis before the age of 16 had a thinner cerebral cortex – the outermost layer of the brain – than those who had not, Canadian researchers discovered.

Experts say the findings are concerning because the cerebral cortex is a crucial part of the brain – responsible for cognition, memory, and reasoning.

The scientists behind the research argue that THC – or tetrahydrocannabinol, the psychoactive substance in cannabis – could be shrinking this section of the brain.

The findings come amid increased scrutiny over the dangers of cannabis smoking. Nearly one in ten people in the UK say they have used the drug in the past year. Among 16 to 24-year-olds, this figure rises to 15 per cent.

Earlier this month, medics in the US, where cannabis use has been legalised in 24 states, said they had seen a surge in debilitating side-effects linked to chronic use of the drug.

This includes a rising number of cases of ‘scromiting’ – a phenomenon where sufferers both scream and vomit.

Prior studies have also linked cannabis use in adolescents to increased risk of developing serious psychotic disorders in later life.

One study from 2007 found that teens who had smoked marijuana at least five times were twice as likely to develop psychosis over the next ten years as those who had never tried the drug.

The latest research looking at the effect of cannabis on the brain was carried out by scientists at the Université de Montréal Faculty of Medicine.

Dr Tomas Paus, psychologist and the study’s co-author, said it was possible that cannabis use may ‘make it harder for the brain to learn new things, interact with people and cope with new situations’.

‘In other words, it makes the brain more vulnerable to everything that can happen in a young person’s life.’