🩺 Researchers establish link between early cannabis use and poor health

According to a study conducted at McGill University, adolescents who start using cannabis early and frequently are more likely to require physical and mental health care in adulthood.

The study shows that people who started using cannabis before the age of 15 and who continued using it daily or almost daily are more likely to need care for depression, anxiety, suicidal thoughts, injuries, and health problems, such as respiratory disorders. In contrast, the study shows that people who started using cannabis after the age of 15 would have more health problems, but only on a physical level.


The study does not allow for the interpretation of these associations, but the researchers point out that different reasons can explain the results.

"Young people under 15 are in a period of intense cognitive development, which can heighten the effects of cannabis on their mental health," explains Massimiliano Orri, assistant professor of psychiatry at McGill University, clinician-researcher at the Douglas Research Centre and holder of the Canada Research Chair in Suicide Prevention.

Prof. Orri specifies that the link is complex: some people use cannabis to cope with existing problems. In contrast, for other people, use can play a role in the emergence of new problems.

"Cannabis can also impair attention capacity and cognitive functions, which in turn can increase the risk of accident-related injuries," he adds.

A first study that associates cannabis use and health care

Using data from the Quebec Longitudinal Study of Child Development, the researchers tracked the cannabis use of a large cohort of children aged 12 to 17 and linked it to the health care they received up to age 23, while taking into account a wide range of early-life factors, such as the environment in which the subjects grew up and how often they used health care services.

"Even after considering several risk factors that existed prior to cannabis use, we found an increased risk of using health services for mental and physical problems among youth who started using cannabis at an early age," reports Pablo Martínez, a postdoctoral researcher at McGill University. "This suggests that cannabis use alone may be implicated in the development of health problems."

When is a child still "too young" to use cannabis?

The study sheds new light on the debate about the age at which cannabis use is less risky, and the results support public health recommendations that young people should avoid using cannabis.

In Quebec, the legal age to buy cannabis (21) is higher than in most other provinces (19) and at the federal level (18). The researchers note, however, that beyond what the law provides, societal evolution and increased accessibility due to legalization may influence use among minors.

"Efforts must be made to discourage the youngest from using cannabis," argues Prof. Orri. "Public health initiatives should target children who are likely to start using early and frequently; they would benefit the most from clinical interventions aimed at reducing long-term risks."