Psychosis is a family of psychiatric disorders that include the most devastating schizophrenia. (iStock)

Cannabis use linked to increased risk of psychosis, warn professors


Scientific studies indicate that using cannabis increases the risk for later development of psychosis such as schizophrenia, and the earlier the use, the greater the risk, warn two professors of psychiatry. Psychosis is a family of psychiatric disorders that produce delusions, auditory hallucinations and bizarre thinking. Schizophrenia is the most devastating.

Six times the risk, reports one study

“One seminal, longitudinal study that followed 45,000 Swedish conscripts over 15 years found a six-fold increase in the risk of developing schizophrenia in those who consumed high amounts of cannabis,” write Ian Gold and Joel Gold, professors of psychiatry at McGill University and the NYU in a newspaper editorial.

Canadian youth have one of the highest rates of cannabis use in the world, according to the UN. (iStock)

The younger, the more vulnerable

“Age is absolutely an issue,” said Ian Gold, associate professor of philosophy and psychiatry at McGill University in an interview. “The earlier you use cannabis the more dangerous it is. We know for example, that kids who start using cannabis at 15 are at greater risk of psychosis than kids who start using at it at 18.”

Not a cause, but likely a factor

That’s not to say that cannabis causes psychosis. It’s not know exactly what causes it. But a study published this year surveyed nearly 100 possible factors and identified cannabis use as one of four factors most definitively linked to the disorder. Other factors include family history, living in a city, being an immigrant and having had difficult experiences in childhood.

Gold said that much more research needs to be done. Now that cannabis has been legalized, he hopes governments will provide more funding and scientists will be more willing to do the research.

In the meantime, he thinks policy-makers must look at effective ways to warn young people about the risks of consuming cannabis.

Young Canadians are big users

Young Canadians have one of the highest rates of use in the world. In 2016, the World Health Organization looked at cannabis use among 15-year olds in 40 countries and found that use by Canadians was the second highest at 13 per cent.

In the same year, the Canadian government’s statistics agency reported that 20 per cent of those between 15 and 19 had consumed cannabis in the past year.

(photo Natalie Stoljar)

Prof. Ian Gold explains the link between psychosis and the consumption of cannabis.
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