The Chief Medical Officer in Colorado, where marijuana was legalized in 2014, has some advice for Canada leading up to the legalization of marijuana on July 1.

Dr. Larry Wolk told Island Morning host Matt Rainnie Canadians have been interested in hearing his opinions on the subject since it was confirmed marijuana legalization was coming to Canada, and to hear what his state's experience has been.

"The short answer is we haven't seen much," said Wolk.

"We haven't experienced any significant issues as a result of legalization."

One in four adults and one in five youth use marijuana on a somewhat regular basis," said Wolk, and those numbers haven't changed since legalization.

More hospital visits

Wolk noted marijuana has caused a few more visits to the ER, but most of those people are visitors, not residents. He credits an extensive education campaign with helping residents use marijuana safely.

On the subject of safety, Wolk cautioned against selling marijuana in liquor stores or bars.

It makes some sense to align the legal age for marijuana and alcohol use, says Dr. Larry Wolk. (Radio-Canada)

"The co-use of marijuana and liquor is a bad idea," he said.

"Marijuana in of itself — or the THC — and alcohol in of itself can cause impairment, and we know that those effects are not just additive but exponentially increased if somebody chooses to co-use both substances."

Health issues versus practical issues

Setting a legal age for use is tricky, said Wolk, because there are both health and practical factors to take into consideration.

"Biologically we know the correct age should be 25," he said.

"Nineteen may be a little too young, I mean because, again, of the developing brain issues, but if that's the legal drinking age and you already have a high prevalence … then it may make sense to align that with the legal drinking age."

In Colorado the legal age for marijuana use is 21, the same as for alcohol.

The Canadian Student Tobacco, Alcohol and Drugs Survey has found that P.E.I. youth already have the highest rates of marijuana use in the country, with about one in four reporting in 2014-15 they had used it in the previous 12 months.

Wolk said there are still unanswered questions about legalization. There has been no increase in recorded impaired driving, but the numbers are difficult to track.

It terms of marijuana being a gateway drug, he said Colorado has seen an increase in heroin-related deaths, but those increases are in line with national trends, and again there is no clear evidence either way.