Citing evidence of the risks to developing brains, the Canadian Psychiatric Association is urging the government to outlaw sales of cannabis to people under the age of 21, and to restrict the quantity and potency of cannabis products that can be purchased by people aged 21 to 25.

The CPA’s position puts them at odds with the Liberals’ task force, which recommended in December that marijuana and other cannabis products be legalized for those 18 or older.

The Liberals’ legislation to legalize recreational pot use is expected to be tabled Thursday.

The CPA says it based its position on the fact that the brain continues to mature until the mid-20s, and research suggests cannabis use interferes with brain development in a multitude of negative ways, including:

  • Aspects of cognition, including attention, memory, processing speed, visuospatial functioning and overall intelligence
  • Increased risk of developing a primary psychotic illness in those individuals who are vulnerable
  • Links between cannabis and depression, anxiety disorders and the onset of other mental illnesses
  • Possible adverse effects on the development of babies whose mothers use it while pregnant
  • An increased likelihood of dependence among those who start using younger.

The Canadian Medical Association, which favours legalization in general, has also recommended that the legal age for marijuana consumption be set at 21 with more potent products restricted until age 25.

The CMA said a position statement issued last fall that 25 would be the “ideal minimum age” for legal purchases but that 25 was unrealistic.

The CMA identified the health harms of marijuana as including:

  • Addiction
  • Cardiovascular effects
  • Pulmonary effects like chronic bronchitis
  • Mental illness
  • Cognitive impairment
  • Higher incidence of psychosis disorders like schizophrenia
  • Injuries from impaired driving

Stocks in companies planning to capitalize on marijuana jumped in December when the Liberals’ task force recommended a minimum age of 18.

Jeffrey Lizotte, CEO of Next Wave brands, said at the time that the stock buying happened because most companies had expected the minimum purchase age to be set at somewhere between 21 and 25.

"Luckily they took a more evidence-based approach,” Lizotte said. “They understand that most consumers are aged 18 to 25, so if you exclude them from this market they'll go to the black market."

Some Conservative MPs have expressed concern about the possibility that cannabis could be legalized for those as young as 18. Leadership candidate Kellie Leitch, meanwhile, would roll back legalization.

Conservative MP Colin Carrie said recently that the government’s priority should be to protect the health and safety of Canadians.

“We know the science is clear,” Carrie said. “For kids up to age 25, the brain is still developing.”