Ethanol and illicit drugs acute use and abuse as risk factors for suicide: A case-control study based on forensic autopsies in the Basque Country, Spain

Introduction: Abuse/dependence and acute use of ethanol and illicit drug are considered risk factors for suicide. The risk is also influenced by demographic conditions and/or psychiatric comorbidity. The aim of the study was to test the association between presence of ethanol, illicit substances and prescribed drugs in suicide decedents and controls.

Materials and methods: Case–control study of autopsies performed in the Biscay Forensic Pathology Service, Basque Country, Spain from 01/01/2010 to 30/06/2021 in subjects between 15 and 55 years old. Suicide deaths (n = 481) with completed autopsy were evaluated. Concurrent natural deaths were chosen as controls (n = 330). The risk for suicide according to demographic, toxicological and psychiatric variables was analyzed using logistic regression.

Results: Ethanol was present in 21% and illicit drugs, mainly cannabis, cocaine and amphetamine, in 27% of suicide deaths. Illicit drugs were more frequent among males. In 63% of suicide cases, prescribed psychotropic drugs were detected.

In a multivariate analysis, the main risk factors for suicide were psychiatric diagnosis of illicit drug abuse/dependence (OR = 5.56, 95% CI 2.74–11.30) or another mental disease as mood or psychotic disorders (OR = 13.05, 95% CI 8.79–19.37). Acute presence of ethanol (OR = 4.22, 95% CI 2.52–7.08), recent use of cocaine (OR = 2.52, 95% CI 1.05–6.07) and age <35 years (OR = 2.50, 95% CI 1.62–3.87) were also associated with suicide deaths.

Conclusions: The presence of drugs of abuse in suicide deaths of people ≤55 years old is high. Recent use of ethanol and cocaine is significantly associated with an increased suicide risk. Specific prevention strategies against exposition to substances of abuse should be promoted, especially in psychiatric patients.