Canadian doctors say it's time to talk about the impacts of marijuana use on health.

The Canadian Medical Association called Thursday for a strong public health approach to legalizing marijuana.

The group aims to:

Prevent drug abuse and dependency.

Ensure assessment, counselling and treatment services are available for those who wish to stop using.

Increase safety for vulnerable groups such as young people, pregnant women and those with psychological and psychiatric illnesses.

In people with psychological and psychiatric illnesses, marijuana can precipitate seizures and in some cases psychosis, said Dr. Granger Avery, CMA president. "That's why we made the recommendations about age and restricting access to certain groups."

As legalization approaches, Dr. Robert Tanguay, a pain psychiatrist in Calgary, is focused on educating people as a form of prevention.

"I think the addiction medicine part of me is saying, 'You know, decriminalization is a good idea and legalization is a good idea,'" said Tanguay. "The psychiatrist in me is saying we have to be careful."

Contrary to perception among some, marijuana isn't neutral or inert in its effect on people, Tanguay said.

What are some of the harms and benefits?

Smoking marijuana can produce chronic bronchitis-like illness.

Cannabis interacts with almost all parts of nervous system and many tissues in the body, said Dr. Harold Kalant, a professor emeritus in the department of pharmacology and toxicology at the University of Toronto's medicine faculty,

Cannabis also increases the heart rate and workload on the heart. Physicians have reported instances of middle-aged men with narrowed arteries having heart attacks within an hour of toking.

"And even more worrying, I think, are young men, men in their early 20s, suffering strokes," Kalant said. The number of published incidents of that happening in the medical literature is small and how it seems to occur isn't yet clear, he said.

Marijuana isn't neutral or inert in its effect on people. (Sean Kilpatrick/Canadian Press)

Another concern is how to regulate against stoned or impaired driving.

Within medicine, the strongest medical marijuana research points to positive effects to:

Relieve chronic pain (lasting three months or more) in adults.

Stimulate appetite in people with cancer, AIDS and other diseases.

Ease nausea and vomiting during chemotherapy.

There are also potential benefits and ongoing clinical trials testing cannabis or its components to:

Relieve muscle spasms in people with multiple sclerosis.

Reduce seizures in children with epilepsy that can't be controlled with existing medication. The extracts contain very low levels of psychoactive THC favoured in recreational pot plants and higher cannabidiol or CBD.

Kalant thinks that when cannabis is legalized, there should be "very clear specification of what the maximum percentages are of THC and the minimum percentages of CBD for both medical and not medical use."

Apart from physical health, experts say legalization offers a chance to increase awareness and education among Canadians of all ages.