Smoking strong cannabis ‘can lead to brain damage,’ study claims

© Steve Dipaola
Smoking extremely strong cannabis can lead to “significant” brain damage, a King’s College London study suggests.

The study, published in the journal Psychological Medicine, found that “skunk” cannabis damages the corpus callosum, a bundle of neural fibers that allows communication between the brain’s left and right hemispheres.

The illegal drug contains high levels of tetrahydrocannabinol (THC), the chemical responsible for the high users receive.

Regular use of the substance can lead to more harm, according to the research.

Frequently smoking the drug could trigger mental health issues, hallucinations and slow down brain activity.

Researchers examined 56 patients who reported having had a psychotic episode and 43 healthy volunteers.

The average age of healthier participants was 27 while the average age of psychotic patients was 29.

Lead researcher Dr Paola Dazzan, from the Institute of Psychiatry, Psychology and Neuroscience at King's College London, said: “We found that frequent use of high potency cannabis significantly affects the structure of white matter fibers in the brain, whether you have psychosis or not.

This reflects a sliding scale where the more cannabis you smoke and the higher the potency, the worse the damage will be.”

Co-author Dr Tiago Reis Marques said: “This white matter damage was significantly greater among heavy users of high potency cannabis than in occasional or low potency users, and was also independent of the presence of a psychotic disorder.”

Commenting on the findings, freelance journalist Rhiannon Lucy Cosslett said legalizing the drug would give users “far greater control and choice” over the strength of what they smoked.

More than two million people in Britain smoked cannabis last year. A private analysis by the Treasury found that legalizing cannabis would raise tax revenues worth hundreds of millions of pounds and result in huge savings for the criminal justice system.

In August, government ministers debated a petition signed by 200,000 people calling for the legalization of cannabis. Its prohibition was upheld, however.