'Quite a few' risks posed by recreational cannabis, researcher warns

A marijuana researcher with the University of Manitoba wants users of recreational marijuana to be aware of the risks.

Marijuana can cause cognitive issues in young people, dependency in some users

Teens who use marijuana face a higher risk of cognitive difficulties and intellectual delays, says an oncologist with Cancer Care Manitoba. (Ben Nelms/Reuters)

Recreational marijuana use comes with risks, especially for young users, a Winnipeg medical researcher and oncologist warns after a task force released recommendations on regulating the sale of the drug.

On Tuesday, the Task Force on Cannabis Legalization and Regulation advised the federal government to limit recreational marijuana to people 18 and older and give provinces the option of imposing an older age limit.

Dr. Paul Daeninck, an oncologist with Cancer Care Manitoba and assistant professor at the University of Manitoba who has studied marijuana use, said people up to age 25 may experience added risks if they use the drug.

Paul Daeninck is an oncologist with Cancer Care Manitoba and assistant professor at the University of Manitoba who has studied marijuana use. (CBC)

"When we hit 18 years of age, we're thought to be mature," he said. "However, our brains still continue to develop, they continue to make new connections, and that can go as long as somewhere between 21 and 25 years of age."

He said young people who use marijuana may experience cognitive difficulties and intellectual delays. The Canadian Medical Association had recommended the minimum age for purchasing cannabis be 21 with strong regulation on access until a person turns 25.

"The trouble with marijuana is that there is some evidence that the use of marijuana at a younger age may cause problems with those neuroconnections," said Daeninck.

Older users also face risks

For older users, Daeninck said there are "quite a few" risks posed by consuming marijuana, whether through smoke or edibles.

"We know looking at the research from the use of recreational marijuana that people can become very drowsy with it," he said, adding for some the effect is a desired one — a state of relaxation.

Daeninck said 10 or 11 per cent of users develop a dependency on marijuana, while alcohol has a 15 to 18 per cent rate of dependency.

"Several years ago we thought marijuana doesn't cause any sort of dependency or abuse problems," he said. "We know now there is a small risk."

Marijuana that's high in tetrahydrocannabinol (THC) can cause hallucinations, episodes of paranoia and psychosis.

Daeninck agreed with the task force's recommendation to tax marijuana that's higher in THC at a higher rate.

Daeninck warned older people with heart problems to avoid using marijuana because it can cause a drop in blood pressure.

Finally, the University of Manitoba researcher warned the various forms of marijuana can affect people in different ways.

When you smoke or vaporize marijuana, for example, the drug takes about seven minutes to take effect. But when you consume the drug in food or drinks, the drug can take a lot longer to kick in — up to an hour and a half.

What's more, the drug's effects last much longer when it's consumed in food — up to 12 hours compared to just two when it's inhaled in smoke or vapour.

The federal government promises to table legislation legalizing recreational cannabis in spring 2017. It could be available for sale in Canada in 2019.