Association between mental health service utilisation and sharing of injection material among people who inject drugs in Montreal, Canada.

BACKGROUND: High-risk injection behaviors are associated with high prevalence of mental health problems among people who inject drugs (PWID). However, whether the use of mental health services is associated with lower risk of sharing injection material remains undetermined. This study aims to examine the association between mental health service utilisation and receptive sharing risk, and determine the potential modifying effect of psychological distress on this association. METHODS: Participants answered an interviewer-administered questionnaire at 3-month intervals gathering information on sociodemographic characteristics, substance use and related behaviors, services utilisation and significant mental health markers. Relationship between the use of mental health services and receptive sharing was modeled using the generalized estimating equation (GEE), controlling for age at baseline, gender, and other potential confounders. Psychological distress was estimated using the Kessler Psychological Distress Scale (K10). Effect modification was investigated by adding an interaction term in the univariate GEE analysis. RESULTS: 358 participants contributed to 2537 visits (median age 40.3, 82% male). Mental health service utilisation was reported in 631 visits (25%), receptive sharing in 321 visits (13%) and severe psychological distress in 359 visits (14%). In multivariate GEE analyses, a significant association was identified between receptive sharing and the use of mental health services (aOR = 0.69; 95% CI = 0.50-0.94). We found no evidence of effect modification by psychological distress. CONCLUSION: Among PWID, mental health service utilisation was associated with lower likelihood of receptive sharing, regardless of level of psychological distress. These findings should be taken into account when designing harm reduction strategies for this population.