Substance use disorders among youth with chronic physical illness.

This study estimated prevalence of substance use disorder in youth with chronic physical illness; quantified magnitudes of association between different chronic physical illnesses with substance use disorder; and, tested whether mental disorder moderates these associations. Data come from 6,377 individuals aged 15-30 years in the Canadian Community Health Survey-Mental Health. Alcohol, cannabis, or other drug use disorder measured using the WHO Composite International Diagnostic Interview 3.0. Individuals with chronic physical illness were more likely to have other drug use disorder compared to healthy controls (2.4% vs. 1.3%; p < .001), but not more likely to have alcohol (7.8% vs. 6.8%) or cannabis use disorder (5.0% vs. 3.6%). Odds of alcohol use disorder were higher among individuals with musculoskeletal conditions, OR = 1.41 (1.03-1.93), but lower among individuals with neurological conditions, OR = 0.49 (0.33-0.72), compared to healthy controls. No associations were found for cannabis use disorder. Odds of other drug use disorder were higher among individuals with endocrine conditions, OR = 2.88 (1.37-6.06). In the presence vs. absence of major depressive disorder, odds for substance use disorder were higher among individuals with respiratory or endocrine conditions. However, odds were lower among individuals with comorbid neurological and major depressive disorders or comorbid respiratory and generalized anxiety disorders. The complexity of the association between chronic physical illness and substance use disorder is compounded when accounting for the moderating effect of mental disorder, which in some contexts, results in a reduced likelihood of substance use disorder in youth with chronic physical illness.