Heavy Marijuana Use in Adolescence is Associated with Disability Later in Life

Heavy marijuana use in adolescence has been associated with a number of negative consequences in adulthood, including psychiatric illness and cognitive impairment. Researchers analyzed a cohort of 49,321 Swedish men who were conscripted into compulsory military service 1969–1970, all of whom completed a psychological assessment and questionnaires on substance use, family and social background, and school performance. The outcome of interest was whether participants were granted a disability pension (DP) between the ages of 20 and 59.

• Nine percent reported marijuana use by age 18; 1.5% reported having done so more than 50 times and were defined as “heavy users.” These participants were more likely to have a psychiatric diagnosis, low emotional stability, low social maturity, and to report unhealthy alcohol or any other drug use.
• Eleven percent of the cohort was awarded a DP by age 59. On unadjusted analysis, any marijuana use was associated with future DP, and was highest for those with heavy use (hazard ratio [HR], 2.58).
• After adjusting for social background, mental function, and health behaviors, only heavy use was associated with future DP (HR, 1.30).

Comments:

It is not particularly surprising that people with marijuana use are more likely to experience disability later in life. The fact that the association almost disappears when taking other factors into account suggests that this is not a causal association, but simply a marker for other factors that lead to disability. Moreover, people with heavy marijuana use only accounted for a small proportion of those receiving DP.

Darius A. Rastegar, MD

Reference:

Danielsson AK, Agardh E, Hemmingsson T, et al. Cannabis use in adolescence and risk of future disability: a 39-year longitudinal cohort study. Drug Alcohol Depend. 2014;143:239–243.