Teenage cannabis use increases risk of adult depression: Research

Up to 60,000 UK cases of adult depression could potentially be avoided if teenagers did not smoke cannabis, new research suggests.

Smoking the drug before the age of 18 is linked with an increased risk of depression and suicide in adulthood, according to a study published in journal JAMA Psychiatry.

The researchers warned cannabis was a significant public health risk, as they called for officials to make tackling use of the drug a priority.

“It’s a big public health and mental health problem, we think,” co-author Professor Andrea Cipriani of Oxford University said.

“The number of people who are exposed to cannabis, especially in this vulnerable age, is very high and I think this should be a priority for public health and the mental health sector.”

The researchers analysed data from 11 studies involving more than 23,000 individuals and described it as the largest meta-analysis to date in this field.

About 7% of cases of adult depression may possibly not occur if teenagers stopped smoking cannabis, they found.

This means at any one time up to 60,000 cases among 18 to 34-yearolds in the UK and 400,000 in the US could be attributable to use of the drug during adolescence, they suggest. However, a link was not found between cannabis exposure and anxiety in adulthood.

While the risk of depression is modest, the researchers said the common use of cannabis among teenagers makes it a concern.

In England about 4% of adolescents aged 11 to 15 are estimated to have used the drug within the last month.

Animal studies have suggested a link between exposure to cannabinoids, the active component of cannabis, and the onset of depressive symptoms in adulthood.

It is thought that cannabis may alter the development of parts of adolescent brains.

The study, by researchers at McGill University and Oxford University, included teenagers who had used cannabis at least once before the age of 18 and did not distinguish between the frequency of use.