A new study has been published based on Irish data comparing characteristics of suicide to non-suicide drug poisoning deaths (NSDPD), by sex.1 Both suicide deaths and drug poisoning deaths are dominated by deaths among men; therefore, absence of sex-stratified mortality data can mask important sex-based differences in the data. 

Introduction

Suicide is a significant public health concern with over 700,000 people worldwide dying by suicide each year. Accurate data on suicide deaths, including the characteristics of those who die by suicide and factors associated with these deaths, are essential to inform effective suicide prevention strategies.2 In Europe, drug poisonings are estimated to account for 9.1% of suicides among young men and 23% of suicides among young women.3 Suicide by drug poisoning is potentially preventable; however, evidence on associated risk factors by sex is limited.

The aim of this study is to determine the extent to which individual and social contextual factors and specific drugs/drug groups are associated with suicide compared with NSDPD, and to determine whether there are differences between men and women in a national Irish study of drug poisoning deaths between 2015 and 2017. 

Methods

Data for this study were extracted from the National Drug-Related Deaths Index (NDRDI). The NDRDI’s definition of a poisoning death is a death directly due to the toxic effect of one or more substances on the body. The suicide drug poisoning deaths (SDPD) group 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 Rosenberg criteria for determination of suicide.4 To be included ‘based on the balance of probabilities’, the death had to be self-inflicted with evidence of intent to die in addition to risk factors for suicide.

Analysis included univariable and multivariable logistic regression to estimate unadjusted and adjusted odds ratios (AOR) and 95% confidence intervals (CI) for factors associated with SDPD (primary outcome) compared with NSDPD and stratified by sex. 

Results

SDPD accounted for 240 (22%) of 1,114 poisoning deaths reported during the period 2015–2017 inclusive, the majority among men (n=147, 61%). Increasing age, especially over 54 years of age (AOR 3.01 [95% CI: 1.68–5.38]), 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

The authors conclude that factors associated with SDPD included being male, older age, mental illness, chronic pain, and history of a previous overdose. The main drugs found to be associated with SDPD included non-opioid analgesics, antidepressants (specifically tricyclic antidepressants), and antipsychotics. Similar effects were observed among men and women in the sex-specific analyses, with small variations in magnitude of effects.

Ongoing monitoring for signs of suicidal intent in individuals with mental illness, chronic pain, overdose, and/or prescribed mental health medications may identify individuals in need of additional intervention. Adequate specialised pain management clinics, with non-pharmaceutical therapy used to complement pharmaceutical therapy, should be resourced. 
 

1  Lynn E, Cousins G, Lyons S and Bennett KE (2022) Comparing characteristics of suicide to non-suicide drug poisoning deaths, by sex, in Ireland. J Affect Disord, 306: 80–89.
https://www.drugsandalcohol.ie/35890/

2  World Health Organization (2014) Preventing suicide: a global imperative. Geneva: World Health Organization.
https://www.drugsandalcohol.ie/22594/

3  Värnik A, Kõlves K, van der Feltz-Cornelis CM, Marusic A, Oskarsson H, Palmer A, et al. (2008) Suicide methods in Europe: a gender-specific analysis of countries participating in the ‘European Alliance Against Depression’. J Epidemiol Community Health, 62(6): 545–551.

4  Rosenberg ML, Davidson LE, Smith JC, Berman AL, Buzbee H, Gantner G, et al. (1988) Operational criteria for the determination of suicide. J Forensic Sci, 33(6): 1445–1456.