Research links teenage marijuana smoking to depression in later life

Smoking marijuana as a teenager increases the risk of depression and suicide later in life, according to a new study published in the journal JAMA Psychiatry.

Researchers from the UK and the US have found that the drug could damage a child’s brain to the degree that it leads to mental health issues later in life. In the largest study of its type to date, mental health experts from McGill University and Oxford University estimated that almost 500,000 adults in the UK and the US would not suffer from mental health disorders had they not smoked marijuana as teenagers.

The research teams warned that marijuana, used by millions of young people, and which is legal in several US states, poses a significant risk to public health and has ‘devastating consequences.’ They request that health officials prioritise tackling the drug’s use by teenagers. The study team attributed the link between teenage marijuana use and depression in part to the higher strength of marijuana available today, compared to the relatively mild strains of the drug available during the 1980s and 1990s.

The researchers from the two universities analysed data from 11 studies, involving more 23,000 people who had used marijuana at least once before the age of 18. The study concluded that about 7% of depression cases in adults would not have occurred if they had stopped smoking marijuana when they were teenagers. The finding means that 60,000 cases of depression among people aged 18 to 34 in the UK and 400,000 cases in the US could be attributed to marijuana use when they were teenagers.