Substance use and self-poisoning in schizophrenia: 11-year findings from a national clinical survey of suicide in mental health patients in England

Suicide is the leading cause of unnatural death among people with schizophrenia. Substance use is a highly prevalent comorbid feature of schizophrenia and a modifiable risk factor for suicide. However, no studies have examined changes in the frequency of substance use or self-poisoning in those who died by suicide over time. Knowing this could support more tailored approaches to reducing specific risk factors and access to means in those with schizophrenia who are at risk of suicide. We conducted an 11-year observational study on a clinical survey of people with schizophrenia in England who died by suicide within 12 months of contact with mental health services between 2010 and 2020 (n = 2718). Overall, alcohol, cannabis and stimulants were the most frequently reported substances. The odds of lifetime use significantly increased over time for cannabis, stimulants, heroin, and benzodiazepines. There were differences in socio-demographic, behavioural and clinical factors between those with recent and historical alcohol and drug use before death. Deaths by hanging, jumping and self-poisoning were the most common suicide methods. Though deaths by hanging significantly increased over time, deaths by self-poisoning significantly decreased, especially by means of psychotropic medication and opioids. To improve risk management, clinical efforts should focus on identifying and treating people with schizophrenia using specific substances. Nationwide initiatives for improving safety in prescribing could be contributing to reduced risks of suicide via self-poisoning in this group.