Youth Who Use Cannabis at Early Age More Likely to Have Health Problems as Adults

McGill study finds youth using cannabis young face higher long-term health risks.

Roxana Gonzalez/Shutterstock

Youth who start using marijuana before the age of 15 have more physical and psychological problems into early adulthood, according to a study by McGill University researchers.

The study used data from the Quebec Longitudinal Study of Child Development, with researchers looking at cannabis use in 1,591 youth between 12 and 17 years old, as well as health care records up to age 23.

Those who began using cannabis before 15 and continued to use it daily or near-daily were more likely to seek help for issues such as depression, anxiety, and suicidal distress, as well as physical problems such as injuries and respiratory problems, according to a statement from McGill.

Those who started using marijuana after the age of 15 were only linked to physical health problems in adulthood.

Assistant professor of psychiatry at McGill and corresponding author Massimiliano Orri said there may be different reasons behind the findings.

“Youth under 15 are in a critical period of brain growth, which may make them more susceptible to cannabis’s effects on mental health,” Orri said in the statement.

Some youth may turn to cannabis to deal with existing problems, he said, while others may find using the drug leads to new problems.

“Cannabis can also impair attention and cognition, which may increase the likelihood of accidents causing injuries,” he said.

Researchers found three cannabis-use patterns: 59.6 percent were nonusers (948 participants), 20 percent began using after age 15, and 20.4 percent began using before age 15.

“Beyond mental health, participants with early-onset and frequent cannabis use showed increased odds of medical care use for physical health conditions, notably injuries and poisonings,” the report authors wrote.

They said the increased risks could be due to neurocognitive and behavioral changes connected to frequent cannabis use.

The study also noted that lifestyle factors of those who use marijuana at an earlier age, such as poor diet and sleep patterns, can “compound these risks over time.”

“These findings underscore the importance of ongoing, systematic monitoring of youth cannabis use and associated health outcomes, especially given the increased accessibility, diversity, and potency of cannabis products that continue to expand in many jurisdictions in North America and internationally,” the authors said.

Recreational cannabis became legal in Canada on Oct. 17, 2018, under the Cannabis Act (Bill C-45), making Canada the first G7 nation to legalize cannabis for recreational use.

According to Statistics Canada, 43 percent of youth aged 16 to 19 reported using the drug once in the past 12 months, an increase from 2022, when 37 percent reported using marijuana at least once in the previous 12 months.

The federal minimum age to buy cannabis is 18 years old, while most provinces set the age at 19, except for Quebec, where the minimum legal age to purchase cannabis is 21.

Study researchers said that shifting social attitudes and easier access to the drug can influence underage use.

“Efforts to steer youth away from consuming cannabis too young are important,” Orri said.

“Public health initiatives should focus on identifying young people likely to start early and use frequently, as they may benefit from clinical interventions to reduce long-term risks.”