Incidence and Predictors of Mental Health Disorder Diagnoses Among People Who Inject Drugs in a Canadian Setting

Introduction And Aims: Limited attention has been given to the predictors of mental health diagnoses among people who inject drugs (PWID) in community settings. Therefore, we sought to longitudinally examine the prevalence, incidence and predictors of mental disorder diagnosis among a community-recruited cohort of PWID.

Design And Methods: Data were derived from two prospective cohort studies of PWID (VIDUS and ACCESS) in Vancouver, Canada between December 2005 and May 2015. We used multivariable extended Cox regression to identify factors independently associated with self-reported mental disorder diagnosis during follow-up among those without a history of such diagnoses at baseline.

Results: Among the 923 participants who did not report a mental disorder at baseline, 206 (22.3%) reported a first diagnosis of a mental disorder during follow-up for an incidence density of 4.29 [95% confidence interval (CI) 3.72-4.91] per 100 person-years. In the multivariable analysis, female sex [adjusted hazards ratio (AHR) = 1.74, 95% CI 1.29-2.33], experiencing non-fatal overdose (AHR = 2.33, 95% CI 1.38-3.94), accessing any drug or alcohol treatment (AHR = 1.68, 95% CI 1.24-2.27), accessing any community health or social services (AHR = 1.53, 95% CI 1.02-2.28) and experiencing violence (AHR = 1.60, 95% CI 1.12-2.29) were independently associated with a mental disorder diagnosis at follow-up.

Discussion And Conclusions: We observed a high prevalence and incidence of mental disorders among our community-recruited sample of PWID. The validity and implication of these diagnoses for key substance use and public health outcomes are an urgent priority.