In the latest instalment of Daybreak's look at the legalization of marijuana, a Montreal clinical psychologist warns early pot smokers are more at risk of "becoming dependant on substances of abuse."

Patricia Conrod, a chair of social pediatrics and a professor of psychiatry at l'Université de Montréal, specializes in youth addiction research.


Patricia Conrod says children as young as 12 who are demonstrating early psychological signs of psychosis accelerate that risk quite dramatically if they use cannabis. (Rebecca Ugolini / CBC)

She also works as a clinical psychologist at the Sainte-Justine Hospital.

Here are key excerpts of her interview with Daybreak host Mike Finnerty.

How addictive is marijuana?

It's not a simple question. It's clear that marijuana has many features that other addictive substances have — it stimulates reward centres of the brain, it has the property that people who use it regularly continue to want to use it. Clearly, there are many people who misuse cannabis. So it is addictive, it's just not as addictive as other substances out there.

Are youth more susceptible to marijuana abuse?

One thing we know is that the earlier the onset and regular use of cannabis use, the more at risk you are for depending on cannabis and other substances of abuse. We haven't fully understood why that is but it's a well-established effect.

There's also a link between familial risk of psychosis and harm from cannabis use. People who have a family history or genetic profile associated with risk for schizophrenia or psychosis are also more at risk of harm from cannabis. Children as young as 12 years of age who are demonstrating early psychological signs of psychosis accelerate that risk quite dramatically if they use cannabis.

At what age should it be legal?

I feel very strongly that if this is going to happen in Canada, it should be done within the context of very, very well thought out evidence-based policies that will reduce substance use and the harm from cannabis use. My criticism is that's not happening, that debate is not happening, that dialogue is not happening.

It has to be a very comprehensive drug strategy. It has to involve laws around legal limit — the higher the legal drinking age, for example, the less harm you see from alcohol in young people. It has to involve advertising laws. In Quebec, we see all kinds of naughty activities around marketing to young people that you would not see in other parts of the world, so we really need to crack down on that kind of thing. And we need to ensure that the regulations we've applied to the alcohol and tobacco industry also apply to the cannabis industry.

Should tax revenue from pot sales be used for public health?

Very little money from alcohol and tobacco at the moment is going back to research or implementation of prevention programs and there are a number of prevention programs that, if implemented across the country, could dramatically decrease substance misuse among young people. That's not being done at the moment.

It's a really important opportunity for us to make sure that the taxes that might be collected from the sale of cannabis are directly diverted towards protecting people and protecting young people from harm. I think that's absolutely necessary.