Characteristics associated with suicide among people who use drugs in Ireland 2015 to 2017: a repeated cross-sectional study

Background: Substance use disorder is widely recognised as important risk factor for suicide. This study aims to identify the characteristics of people who use drugs who died by suicide in Ireland in order to inform appropriate prevention measures.

Methods: This is a population based observational study using mortality data from the Irish National Drug-Related Deaths Index, 2015 to 2017. Suicide deaths (SD) had a verdict of suicide or met the criteria for suicide on the balance of probability. Descriptive univariate analysis was used to identify variables to include in logistic regression models. Separate models were run for different drug-user groups.

Results: 1,190 deaths were included: 449 (38%) were SD and 741 (62%) were non-suicide deaths (NSD). Hanging was the main cause of death among SD (293, 65.3%). Poisoning was the main cause of death among NSD (588, 79.4%). Logisic regression showed that characteristics of SD deaths compared to NSD were: mental health problems (OR 7.4, 95% CI 5.2-10.6); female (OR 1.7, 95% CI 1.2-2.5); previous overdose (OR 2.1, 95% 1.3-3.5); cocaine use only (OR 11.5, 95% CI 7.6-17.4); and other drug use excluding cocaine or opioids (4.0, 95% CI 4.9 -10.2). As 54% of SD and 70.5% of NDS used more one drug, separate models were run for opioid users; cocaine users; and other drug users excluding opioids and cocaine. Mental health problems were significant with SD for all three groups (all P<0.000). History of previous overdose was significant for opioid users and other drug users.

Conclusion: The study’s strength is that includes both deaths which met the legal definition of suicide and those on the balance of probability. Use of cocaine, other drugs, and mental health problems are significant factors in suicide deaths among people who use drugs in Ireland.