Alcohol and cocaine use prior to suspected suicide – Insights from toxicology

Problem

Alcohol and illicit drug use are major modifiable risk factors for suicide, the leading cause of death for men under the age of 49 and women under the age of 34 in the United Kingdom. Data currently available in the UK on substance use in suicide is limited to patients in contact with secondary psychiatric services, which accounts for only 28% of suicide decedents. This leaves a majority who never approach services, or are excluded due to substance misuse – and suggests a gap in our understanding of substance misuse in suicide. Post-mortem toxicology identifies all decedents regardless of contact with psychiatric services and becomes vital to understand substance use prior to methods such as hanging, which is common, highly lethal, and difficult to study in living populations.

Approach

In England and Wales, all violent or unnatural deaths (including suicides) are referred to the Coroner. As part of the pathologist’s investigation into the cause of death, toxicological analysis may be requested. The Toxicology Unit, Imperial College London, performs toxicological analysis on post-mortem samples submitted by pathologists on behalf of Coroners. All cases in the Toxicology Unit’s database between 2012 and 2016 were retrospectively assessed for inclusion criteria. We considered all decedents who died from self-injury when the act appeared deliberate and self-inflicted. Femoral blood alcohol concentration (BAC) and presence of cocaine or benzoylecognine (a metabolite of cocaine) in blood and/or urine were tabulated and odds ratios calculated.

Findings

1722 decedents met inclusion criteria. BAC was ≥50 mg/dl in 29% of decedents. Cocaine was detected in 8.4% of all cases and 16.6% of those who also tested positive for alcohol. The likelihood of testing positive for cocaine increased with BAC and was most frequent between 100 and 199 mg/dl, consistent with moderate to severe intoxication (OR 5.88, 95% CI 3.80, 9.09; P ≤0.001) compared to those with BAC <10 mg/dl. Comparing these findings to other studies, cocaine use in our population is far higher than other areas with comparable reported cocaine use such as Australia and Colorado.

Consequences

Here we have demonstrated that alcohol use is a part of many suicides by self-injury and that cocaine use is more common among suicide decedents in comparison to the level of use reported in the general population (0.3% report being frequent users). The work of this study highlights the need to reconsider the lack of emphasis given to substance use in many national suicide prevention strategies as well as the need for increased public education about, and public health interventions to address alcohol and cocaine use in suicidal acts. Clinically, we hope it will energise engagement with depressed or suicidal patients about their alcohol use, and lead to enquiries about both infrequent and habitual cocaine use.