A mental health executive from Steinbach says just because cannabis will become legal in Canada later this year doesn't mean it's good for you. Chris Summerville, Chief Executive Officer of the Schizophrenia Society of Canada, says it can, in fact, do a lot of harm. He explains, people who have a history of mental illness in their family or who have mental health problems, have a 5 to 7 times greater risk of developing psychosis, often leading to schizophrenia.

Chris Summerville"Psychosis is when you have hallucinations like hearing voices that are not there or you have fixed thoughts that have no basis in reality, like believing that the aliens are about to take over the earth."

Summerville adds cannabis has its greatest negative impact on the developing brain up to age 25.

"That's because the young brain is developing in the pre-frontal cortex, in the white matter. Our brains actually have what is called endocannabinoid receptors. When you take cannabis with high THC levels, that affects the endocannabinoid receptors in your brain, leading to psychosis, the hallucinations or delusions."

Summerville says this makes it especially important to try and prevent the use of cannabis before the age of 25, although it can also have these effects on people beyond that age.

"What I would be concerned about if I had a young child or a teenager would be, the earlier you use cannabis and the frequency of that use and also the potency of the THC, the greater the risk of developing depression, anxiety, suicidal ideation as well as psychosis. But, certainly, I've known people in their 40's and 50's who have used cannabis and have developed psychosis, leading to schizophrenia."

Summerville says there is no way Canada is ready for the legalization of cannabis because so many issues have not been properly discussed with the public. In addition to mental health concerns, he says there are concerns about drug-impaired driving and the ability of police to test people for drugs.