Young people who begin using cannabis before age 15 and continue frequent use are significantly more likely to require medical care for both mental and physical health conditions in early adulthood, according to new research.
A comprehensive study published in JAMA Network Open followed 1,591 individuals from birth to age 23 in Quebec, Canada, revealing stark differences in healthcare utilisation based on adolescent cannabis consumption patterns.
The participants, born in 1997-1998, were using cannabis during their teenage years between 2009-2015, before Canada legalised cannabis in October 2018. This means they were accessing cannabis through illegal channels during the study period.
The research identified three distinct groups: those who never used cannabis during adolescence (59.6%), those who began use after age 15 with infrequent consumption (20%), and those who started before age 15 with frequent use (20.4%).
Participants in the early-onset, frequent-use group showed a 51% higher likelihood of seeking mental health care and an 86% increased chance of requiring treatment for physical health conditions compared to non-users.
“The risk is concentrated among those who start early and use frequently,” explained lead author Dr Massimiliano Orri from McGill University.
The study’s findings remained significant even after researchers controlled for 32 individual, family, and community-level factors that could influence health outcomes, including socioeconomic status, family dysfunction, parental substance use, and childhood behavioural issues.
Physical health problems among early users included respiratory conditions, injuries, poisoning, and various other medical issues. Mental health concerns encompassed common disorders such as depression and anxiety, as well as substance-related disorders.
Notably, those who began cannabis use later in adolescence showed no increased risk for mental health problems but did demonstrate higher rates of physical health issues requiring medical attention.
The research utilised data from the Quebec Longitudinal Study of Child Development, linking self-reported cannabis use patterns during adolescence to objective medical records from Quebec’s universal healthcare system between ages 18 and 23.
The study’s authors suggest that early cannabis exposure during critical brain development periods may disrupt normal neural maturation, particularly in areas responsible for executive functioning and emotional regulation.
Whilst the findings highlight the risks associated with early cannabis use, recent evidence suggests that reform may actually help protect young people. Research from Germany following its 2024 cannabis legalisation shows that youth consumption amongst 12-17 year-olds declined from 6.7% to 6.1%, contradicting concerns that legalisation increases adolescent use. Cannabis legalisation, when combined with robust age restrictions and prevention initiatives, can help limit youth access whilst improving public health outcomes, suggesting that well-regulated legal cannabis markets, rather than prohibition, may offer better protection for teenagers.
