Adolescent Cannabis Use Has a Dose-Response Association with Adverse Social Outcomes in Adulthood
Whether adolescent cannabis use causes adverse social outcomes or whether it is merely a marker of other causes is not clear from existing research. Investigators in New Zealand studied a birth cohort of 1003 subjects born in 1977 to determine the association between cannabis use from ages 14 to 21 and education, income, employment, relationship quality, and life satisfaction at age 25. Potential confounding factors, including socioeconomic status, family functioning, exposure to child abuse, childhood and adolescent adjustment, early adolescent academic achievement, and comorbid mental health and substance use disorders were prospectively measured and adjusted for in the final analyses. Subjects were divided into 6 groups based on self-reported cannabis use ranging from no use to use on greater than 400 occasions.
- Subjects demonstrated statistically significant linear trends for decreased university degree attainment, decreased income, increased welfare dependence, increased unemployment, decreased relationship satisfaction, and decreased life satisfaction with increased cannabis use in adolescence.
- This dose-response relationship was consistent for all outcomes in unadjusted and adjusted analyses regardless of whether cannabis categories were based on total times used, average annual frequency, or age periods (14–21 years or 14–18 years).
Although these findings may be subject to reporting bias and may not be immune to residual confounding, the results demonstrate a consistent dose-response association between adolescent cannabis use and subsequent adverse social outcomes, even when adjusted for pre-existing factors. Complete evidence for a causative biologic mechanism will require similarly strong studies in other populations at different ages as well as studies with more direct measures of cannabis use and its consequences than self-reports.Alexander Y. Walley, MD, MSc
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