Importance: Determining the association between drug use and suicide is complicated but can help to inform targeted suicide prevention strategies.
Objective: To examine the substances prevalent in poisoning- and nonpoisoning-related suicides in Australia.
Design, setting, and participants: This was a multiple-year, cross-sectional study of suicides from July 2013 to October 2019 in Australia with toxicology data available in a national coronial database. The cause of death was classified as poisoning related if any type of poisoning was determined by the coroner to contribute to the cause of death. Prevalence ratios (PRs) were calculated to compare substance detection in poisoning- vs nonpoisoning-related suicides. Data were analyzed from October 2021 to April 2023.
Exposures: All substances detected in decedents at the time of death according to toxicology reports were recorded.
Main outcome(s) and measure(s): The most common individual substances and substance classes were identified. From these, blood concentrations of substances of interest were analyzed, and the most commonly occurring combinations of substance classes were listed.
Results: Toxicology was performed on 13 664 suicide decedents (median [IQR] age, 44 [31-57] years; 10 350 male [76%]). From these, 3397 (25%) were poisoning-related suicides (median [IQR] age, 50 [38-63] years; 2124 male [63%]). The remainder were classified as nonpoisoning-related suicides (median [IQR] age, 42 [29-55] years; 8226 male [80%]). PRs for common medicine classes being detected in poisoning-related suicides compared with nonpoisoning-related suicides were as follows: antidepressants (PR, 1.63; 95% CI, 1.54-1.73), benzodiazepines (PR, 2.01; 95% CI, 1.90-2.13), nonopioid analgesics/anti-inflammatory drugs (PR, 1.88; 95% CI, 1.78-2.00), and opioids (PR, 2.72; 95% CI, 2.58-2.87). Alcohol (as ethanol ≥0.03 g/100 mL) was almost equally prevalent in poisoning- and nonpoisoning-related deaths (PR, 1.07; 95% CI, 1.01-1.14), whereas amphetamines (PR, 0.68; 95% CI, 0.61-0.77) and cannabinoids (PR, 0.67; 95% CI, 0.60-0.74) were detected more often in nonpoisoning-related suicides. Combinations of multiple sedative agents in poisoning-related suicides were common.
Conclusions and relevance: Both poisoning- and nonpoisoning-related suicide deaths featured a high prevalence of psychotropic medicines or potential intoxication, which suggests the association of suicide with poor mental health and substance misuse. Findings suggest that substances with a high involvement in poisoning-related suicides should be prescribed cautiously, including antidepressants that are toxic in overdose, sedatives, opioids, and potentially lethal combinations.