Cannabis use in adolescents linked to depression

Experts should not overlook the risks badociated with cannabis use among adolescents.

British and Canadian researchers said they found "strong" evidence linking a case of depression in 14 children under 35 years old to the use of this drug in adolescence, although no definitive proof has been provided.

They said the results should serve as a warning to families who consider cannabis use as part of the growth process.

The team added that brain development was particularly likely.

Researchers – from Oxford University and McGill University in Montreal – have stated that cannabis use among young people is an "important public health problem".

About one in nine adults and adolescents use drugs each year in England and Wales.

The author of the report, Professor Andrea Cipriani, admitted that some parents had a relaxed attitude towards the drug, but added that the evidence was clear.

"It's important information for parents and teens, the risk is modest, but it can have a devastating impact."

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What is the risk level of cannabis?

It is the first time that the real risk is quantified in this way.

The team reviewed 11 previous studies, covering more than 23,000 youth.

Youth who had already had signs of depression or who had a family history were excluded.

It was found that cannabis use before the age of 18 years increased by 37% the risks of developing depression in young adults – defined before the age of 35 years.

How many cases could be avoided?

Researchers estimate that about 7% of cases – one in 14 – could be avoided in young adults if people did not use cannabis in adolescence.

Given that about 8% of this age group suffers from depression, this would amount to 60,000 cases in the United Kingdom, 25,000 in Canada and more than 400,000 in the United States.

The study also examined whether there was an badociation with anxiety and suicide attempts.

The risk of anxiety was increased among young adults, but this was not considered statistically significant.

On the other hand, those who used cannabis in adolescence were three times more likely to commit suicide – although data on this trend was not considered reliable enough to draw definitive conclusions.

So is this proof?

The researchers were unable to prove that cannabis use was definitely at the root of the depression.

Instead, they could only say that it seemed like a strong link.

It's because of the numbers they found, but also from what we know about the impact of cannabis on brain development.

Evidence suggests that the drug affects the parts of the brain that govern rational and emotional thinking, as well as serotonin levels that affect mood.

To prove the connection, trials should be conducted on young people – something that will never be done because it is unethical.

Professor Sir Robin Murray, a psychiatrist at King's College in London, said the research could not be considered conclusive, but acknowledged that the results were "probably correct".

He added that the risk of developing depression was lower than what has already been established for schizophrenia-type psychosis.

He also stated that it was likely that any risk would also be related to the amounts of cannabis consumed and the force – something that this study could not clear.