Teenagers Who Use Cannabis Too Early Have More Health Problems In The Future

This study followed young people from birth to age 23 and showed that starting cannabis use before age 15 and using it frequently is associated with a greater need for medical care for mental and physical health problems in young adulthood. Late use did not increase mental health problems, but was linked to more physical problems. The results highlight the importance of delaying and reducing cannabis use in adolescence.

Adolescence is a period when the brain is still developing. At this stage, areas related to emotional control, decision-making, and risk-taking behavior are still maturing. Therefore, intense experiences, such as the use of psychoactive substances, can have more lasting effects than when they occur in adulthood.

Cannabis is one of the most widely used substances among adolescents worldwide. In countries like Canada, where its use has been legalized, a significant proportion of young people between 12 and 15 years old report having used cannabis at least once in the last year. Furthermore, current products tend to be more potent than in the past, which can increase health risks.

The study followed over 1,500 people from birth to age 23 and identified three groups: young people who never used cannabis, young people who started using it after age 15, and young people who started before age 15 and used it frequently. The results show that this last group, early and frequent users, are the most vulnerable to health problems later in life.

Young people who started using cannabis early and frequently were more likely to need medical attention for mental health problems in young adulthood. This includes anxiety, depression, and other common mental disorders. These findings reinforce previous evidence that early use can increase the risk of psychological distress in the future.

In addition to mental health, early and frequent cannabis use was also associated with more medical visits for physical problems. These include injuries, intoxications, and other illnesses.

Even adolescents who started using it later, after age 15, showed greater use of health services for physical problems, although not for mental health.

One strength of the study is that it took into account many factors that could confound the results, such as family environment, socioeconomic conditions, and childhood characteristics. Furthermore, instead of relying solely on participant self-reported information, the researchers used official health records, making the data more reliable.

The findings don't say that every teenager who uses cannabis will have problems in the future, but they do show that starting early and using frequently increases the risks. This reinforces the importance of public policies, education, and prevention focused on delaying the onset of use and reducing intensity, protecting long-term mental and physical health.

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Health Service Use Among Young Adults With a History of Adolescent Cannabis Use

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

JAMA Network Open. 28 October 2025;8;(10):e2539977.

DOI: 10.1001/jamanetworkopen.2025.39977

Abstract:

Adolescent cannabis use is a substantial public health concern given its associations with adverse mental and physical health outcomes. Understanding how distinct use patterns are associated with medical care utilization in young adulthood is critical for prevention. To examine the association between patterns of adolescent cannabis use and medical care utilization for mental and physical health conditions in young adulthood. This population-based birth cohort study linked to population-wide administrative medical care databases was conducted in the Province of Québec, Canada. Participants included individuals recruited for the Québec Longitudinal Study of Child Development, followed up from birth (1997-1998) to 23 years of age (2021). Data were analyzed November 2023 to February 2025. Self-reported past 12-month cannabis use at ages 12, 13, 15, and 17 years. Medical care utilization for any mental disorder (including common mental disorders and substance-related disorders), suicide-related behaviors, and any physical health condition (including respiratory diseases, injuries and poisoning, and other physical diseases) between ages 18 and 23 years. Analyses were adjusted for 32 individual, family, and community-level confounders measured from birth to younger than 12 years of age using overlap weights. Data for 1591 individuals (818 female [51.4%]; mean [SD] age at first exposure assessment, 12.1 [0.3] years) were analyzed. Three distinct adolescent cannabis use patterns were identified via group-based trajectory modeling: nonuse (948 [59.6%]), late-onset use (318 [20.0%], initiating after age 15 years), and early-onset and frequent use (325 [20.4%], initiating before age 15 years). In fully adjusted analyses, individuals with early-onset and frequent use had significantly higher odds of medical care utilization for any mental disorder (odds ratio [OR], 1.51 [95% CI, 1.10-2.08]), common mental disorders (OR, 1.57 [95% CI, 1.12-2.21]), any physical health condition (OR, 1.86 [95% CI, 1.30-2.67]), injuries and poisoning (OR, 1.41 [1.05-1.89]), and other physical diseases (OR, 1.47 [95% CI, 1.08-1.98]), compared with individuals with no use. Individuals with late-onset use did not differ significantly from those with nonuse for mental health outcomes (OR, 1.13 [95% CI, 0.80-1.58]) but had higher odds of medical care utilization for any physical health condition (OR, 1.63 [95% CI, 1.16-2.28]). Findings of this birth cohort study indicated that early-onset and frequent cannabis use was associated with greater medical care utilization for both mental and physical health conditions in young adulthood. These findings support the relevance of delaying initiation and reducing intensity of cannabis use during adolescence.