Licit and illicit substance use among people who inject drugs and the association with subsequent suicidal attempt

AimTo estimate associations between recent licit and illicit substance use and subsequent suicide attempt among people who inject drugs (PWID). DesignSecondary analysis of longitudinal data from a prospective cohort study of PWID followed bi-annually between 2004 and 2011. SettingMontreal, Canada. ParticipantsSeven hundred and ninety-seven PWID who reported injection drug use in the previous 6months, contributing to a total of 4460 study visits. The median number of visits per participant was five (interquartile range: 3-8). MeasurementsAn interviewer-administered questionnaire eliciting information on socio-demographic factors, detailed information on substance use patterns and related behaviours, mental health markers and suicide attempt. The primary exposure variables examined were past-month use of alcohol [heavy ( 60 drinks); moderate (one to 59 drinks); none], sedative-hypnotics, cannabis, cocaine, amphetamine and opioids [regular ( 4 days); occasional (1-3days); none]. The outcome was a binary measure of suicide attempt assessed in reference to the previous 6months. FindingsIn multivariate analyses, a positive association was found among licit substances between heavy alcohol consumption [adjusted odds ratio (AOR)=2.05; 95% confidence interval (CI)=1.12-3.75], regular use of sedative-hypnotics (AOR=1.89; 95% CI=1.21-2.95) and subsequent attempted suicide. Among illicit substances, occasional use of cannabis (AOR=1.84; 95% CI=1.09-3.13) had a positive association with subsequent suicide attempt. No statistically significant association was found for the remaining substances. ConclusionAmong people who inject drugs, use of alcohol, sedative-hypnotics and cannabis, but not cocaine, amphetamine or opioids, appears to be associated with an increased likelihood of later attempted suicide.