Researchers say the minimum legal age to buy and consume recreational cannabis should be 19 years old.

The findings were revealed on May 14 in a study conducted by a team from the Memorial University of Newfoundland.

“What may be surprising is that several later life outcomes (mental health, general health, and cigarette smoking) from starting cannabis use at age 19 are not different than starting at or after age 21,” says lead author Hai Nguyen.

Determining the appropriate minimum legal age (MLA) for cannabis use has been a matter of huge debate since legalization.

Across Canada, Quebec is the strictest with the age limit set to 21, while the age to buy cigarettes and alcohol is 18. Other provinces have set 19 as the minimum age, there has been pressure to increase it to 21 in Ontario. Alberta, meanwhile, has the lowest age limit at 18 years of age.

The inconsistency and ongoing discussion prompted the researchers to look into it. For the study, 40,000 Canadians aged between 21 and 65 years were examined over the course of 12 months. The team analyzed the association between the age that participants first used cannabis and four later life outcomes: educational attainment, cigarette smoking, self-reported general and mental health. Other factors examined were the demographic characteristics, cigarette smoking status and use of other tobacco products.

“We found different MLAs for different outcomes: 21 for educational attainment, 19 for cigarette smoking and mental health and 18 for general health. Assuming equal weight for these individual outcomes, the ‘overall’ MLA for cannabis use was estimated to be 19 years,” Nguyen points out.

The study also found that when it comes to smoking, participants who first used cannabis between the ages of 19-20 were less likely to smoke cigarettes later in life than those who first used cannabis at age 18. “But no significant difference was found in those who started using cannabis at an older age, indicating an optimum legal age of 19,” the study notes.

But there’s an interesting, potentially negative sidenote to their findings: Those who start using cannabis at younger ages may not attain higher level of education. Survey participants who started using cannabis at 19 had less education than those who started at 21 or later. If cannabis is the cause and not just a correlation, the researchers suggest the MLA should be 21.

Nguyen says, “This is consistent with the medical community’s concern that cannabis use negatively affects cognitive development, which in turn might adversely affect education attainment later on.”