Prevalence and incidence of mental disorders among First Nations and other individuals using methamphetamine in Manitoba, Canada

Methamphetamine use can precipitate or exacerbate mental health disorders. In Winnipeg, Canada, First Nations are at particular risk of harms associated with addiction and mental illness. This study examines the prevalence and incidence of comorbid mental health disorders among First Nations and other Winnipeggers using methamphetamine.

Using population-based administrative health data, we identified First Nations and all other Winnipeg (AOW) residents who had a methamphetamine-related health system contact between 2013 and 2020 (cases) and created control groups that were matched on age, sex, and postal code. We then determined five-year prevalence and one-year incidence of mood, psychotic, personality, and non-amphetamine substance use disorders, in each group. Differences between cases and controls were analyzed using generalized linear regression models after applying high-dimensional propensity score matching to account for potential confounding variables.

4,796 cases and 43,916 controls were included in the study. Both First Nations and AOW with a methamphetamine-related health system contact had higher five-year prevalence (First Nations odds ratio [OR]: 1.92, 95% confidence interval: 1.69-2.18, AOW OR: 3.38, 95% CI: 3.01-3.79) and one-year incidence (First Nations rate ratio (RR): 2.42, 95% CI: 1.88-3.10, AOW RR: 1.83, 95% CI: 1.53-2.20) of mental health disorders vs. their respective comparison group. The baseline five-year prevalence of mental health disorders was higher in the First Nations control group (51.8%) than in the AOW group (38.4%).

Methamphetamine use is associated with a higher prevalence of mental health disorders and the baseline prevalence of mental health disorders is disproportionately high among First Nations.