Alberta Health Services is suggesting a minimum age of 21 for recreational marijuana purchases — and proposes the province use future legislation as an ''opportunity" to consider raising the ages to buy tobacco and liquor.

The organization, which is responsible for delivering health services to Albertans, suggests that setting conservative rules at the outset is the best approach, since it's "very difficult" to tighten rules once they're already in place.

The suggestion comes about 10 months before it's expected marijuana will be legalized for recreational use in Canada. It's up to the provinces to establish their own rules on how cannabis should be sold and distributed — and for what price.

"Delaying use is one of the best ways to reduce the risk of harm to the developing brain," writes AHS in its submission to the Alberta cannabis secretariat.

The submission says science-based, minimum age recommendations are usually in the range of early- to mid-20s. But it also recognizes the government must consider factors such as enforcement, the black market, and public acceptance.

Many have argued that if the government sets the minimum age too high, it will encourage a black market for underage purchasers.

In American states that have legalized marijuana, 21 is the standard minimum age, says AHS.

The organization declined an interview request from CBC.

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The provincial government is expected to release a draft Alberta cannabis framework this fall. (Marcio Jose Sanchez/Associated Press)

Alberta cannabis framework in works

The province received thousands of submissions this summer on its future cannabis legislation. It expects to release a draft cannabis framework in the coming weeks. The framework will inform future legislation.

Submissions came from a range of organizations, from health groups to industry organizations. Their points highlight the potentially conflicting health, social, and economic impacts of marijuana legalization.

A cluster of Alberta industry associations, for example, all support 18 as the minimum marijuana age. Alberta is one of three provinces where people can legally drink alcohol at 18.

"To limit the illegal trade in cannabis, the government of Alberta must ensure that Albertans over the age of 18 who want to consume cannabis have convenient access to these products, regardless of where they live," wrote the Alberta Hotel and Lodging Association.

The association said the government must also ensure "the supply of regulated cannabis is sufficient to meet consumer demand."

Alberta Justice and Solicitor General, the ministry responsible for cannabis legislation, declined an interview for this story.

'Great time' to re-examine other age limits 

Russ Callaghan

Russell Callaghan is a professor at the University of Northern British Columbia who studies alcohol and drug policies in Canada. (Supplied, UNBC)

The idea of raising the minimum age for other substances makes sense, said Russell Callaghan, an associate professor in the northern medical program at the University of Northern British Columbia.

"I think it's a great time to re-examine some of those other age limits for tobacco and alcohol," Callaghan said.

"I sense they will be bundled together at the same age," he said. "It will probably make it easier for them administratively and it will probably make it more coherent administratively ... If they're advocating an age of 19 for cannabis, there would be some leverage to move those other ages up as well."

Callaghan's research has shown that age-based restrictions on alcohol have had a "powerful impact" on limiting alcohol-related harms, such as motor-vehicle accidents, drunk-driving convictions, and visits to hospital rooms.

But it's not clear if the same thing would happen with cannabis.

"The biggest concern for cannabis from a medical and public health perspective is the impact on impaired driving and individuals who are susceptible to and [who have] a family history of individuals with psychotic disorders ... that it may facilitate a persistent psychotic syndrome."

The Alberta Medical Association also supports a minimum age of 21 for marijuana purchases. 

"Legalizing recreational cannabis at an age of 18 knowing the clear effects on the developing brain and higher risk of addiction at younger ages is inappropriate,"  the AMA wrote in its submission.

"It sends a message that there is no increase in risk and harm to youth which is clearly incorrect."