Comparing characteristics of suicide to non-suicide drug poisoning, by sex, in Ireland.

Background: Suicide by drug poisoning is potentially preventable; however, evidence on associated risk factors by sex is limited. The aim of this study is to assist in understanding the extent individual and social contextual factors, and specific drugs influence risk of suicide compared to non-suicide drug poisoning deaths, and how this differs by sex.

Methods: Data were extracted from the National Drug-Related Deaths Index (NDRDI). The study population comprised of deaths which met the NDRDI criteria for the years of death 2015 to 2017 inclusive. Suicide drug poisoning deaths (SDPD) includes all drug poisoning deaths that met both the narrow (‘beyond reasonable doubt’) as recorded by the coroner, and broad (‘based on the balance of probabilities’) definitions of suicide. Suicide based on the balance of probabilities was identified using the Rosenburg criteria for determination of suicide.

Analysis included univariate and multivariable logistic regression to estimate unadjusted and adjusted odds ratios (OR) and 95% confidence intervals (CI) for factors associated with SDPD (primary outcome) compared with non-suicide drug poisoning deaths (NSDPD) and stratified by sex.

Results: SDPD accounted for 240 (22%) of 1114 poisoning deaths, the majority among men (n = 147, 61%). Increasing age, mental ill health (AOR 7.85, 95% CI: 5.46-11.28), chronic pain (AOR 5.57, 95% CI: 3.28-9.46), and history of previous overdose (AOR 5.06, 95% CI: 3.39-7.56) were associated with increased odds of SDPD, with similar results for both sexes. The main drugs associated with SDPD were non-opioid analgesics (OR 4.06 [95% CI 2.66 – 6.18]), antipsychotics (OR 2.42 [95% CI 1.63 – 3.60]) and antidepressants (OR 2.18 [95% CI 1.59 – 2.97]). Pregabalin was associated with SDPD among women only.

Conclusions: Ongoing monitoring for signs of suicidal ideation in individuals with mental illness, chronic pain, overdose, and/or prescribed mental health medications may identify individuals in need of additional intervention.