Researchers found that people who began using cannabis regularly before the age of 15 were more likely, as young adults, to seek treatment for depression, anxiety, suicidal thoughts, and physical health issues.
Young people who begin using cannabis at an early age and continue to use it frequently may face greater health challenges as they move into adulthood, according to a new study led by researchers at McGill University.
The researchers reported that individuals who started using cannabis before the age of 15 and went on to use it daily or almost daily were more likely to seek medical care for mental health concerns, including depression, anxiety, and suicidal distress, as well as for physical issues such as breathing problems and injuries. In comparison, those who first used cannabis after age 15 showed an increased likelihood of physical health problems later in life, but not mental health-related care.
The study does not draw conclusions about cause and effect, but the researchers note that the mental and physical health patterns observed may reflect different underlying factors.
“Youth under 15 are in a critical period of brain growth, which may make them more susceptible to cannabis’s effects on mental health,” said Massimiliano Orri, Assistant Professor of Psychiatry at McGill, clinician-scientist at the Douglas Research Centre and Canada Research Chair in Suicide Prevention.
The relationship is complex, he added. Some people may use cannabis to cope with existing problems, while for others, the drug may play a role in the development of new ones.
“Cannabis can also impair attention and cognition, which may increase the likelihood of accidents causing injuries,” he said.
First study to link cannabis to health care records
Using data from the Quebec Longitudinal Study of Child Development, the researchers followed patterns of cannabis use in a large group of participants from ages 12 to 17 and connected this information to their health care records through age 23. Their analysis took into account many early life influences, including the conditions in which children grew up and how frequently they required medical care during childhood.
“Even when we considered several pre-existing risk factors for cannabis use, we still found increasing risks of using healthcare services for mental and physical health problems for youth with early-onset cannabis use,” said Pablo Martínez, postdoctoral fellow at McGill. “That suggests cannabis itself may play a role.”
What age is ‘too young’ for cannabis?
The study adds new evidence to ongoing debates about when cannabis use becomes risky, backing public health advice for young people to delay the use of cannabis.
In Quebec, the legal age to buy cannabis is 21, stricter than the federal minimum of 18 and the age of 19 in most provinces. Researchers caution that, beyond legal rules, shifting social attitudes and easier access since legalization can still influence underage use.
“Efforts to steer youth away from consuming cannabis too young are important,” said Orri. “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.”
Reference: “Health Service Use Among Young Adults With a History of Adolescent Cannabis Use” by Pablo Martínez, Nicholas Chadi, Natalie Castellanos-Ryan, Francis Vergunst, Marc Dorais, Jean R. Séguin, Frank Vitaro, Caroline Temcheff, Richard E. Tremblay, Michel Boivin, Sylvana M. Côté, Marie-Claude Geoffroy and Massimiliano Orri, 28 October 2025, JAMA Network Open.
DOI: 10.1001/jamanetworkopen.2025.39977
Funding was provided by the Canadian Institutes of Health Research.
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1 Comment
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