Access to means of lethal overdose among psychiatric patients with co-morbid physical health problems: analysis of national suicide case series data from the United Kingdom

Background: Many physical health problems are associated with elevated suicide risk whilst also providing access to means of overdose. We aimed to investigate whether psychiatric patients with physical co-morbidities who die by suicide were more likely than those without co-morbidities to self-poison with non-psychotropic medications. Methods: We analysed data on 14,648 psychiatric patients who died by suicide in England & Wales during 2004-2015, as recorded by the National Confidential Inquiry into Suicide and Safety in Mental Health. Using logistic regression models adjusted for age, gender, ethnicity, and primary drug dependence/misuse we compared patients diagnosed with physical co-morbidities versus those without to assess whether a greater proportion of the former had died by overdose, and medication prescribed to treat such disorders (e.g. opioids, insulin). Results: 24% (n=3525) were recorded as having physical co-morbidity. A greater proportion of these individuals died by self-poisoning than those without physical co-morbidity (37% vs. 20%, p<.001; adjusted OR 2.47; 95% CI 2.26-2.70), and they were more likely to have used medications for a physical health disorder in overdose (50% vs. 34%; adjusted OR 2.10; 95% CI 1.80-2.46), particularly opioids (30% vs. 22%; p<0.001), paracetamol/opioid compounds (11% vs. 7%, p<.001) and insulin (4% vs. 1%, p<.001). Limitations: Use of survey data may have resulted in under-reporting of physical health problems and/or overdose medications. Conclusions: Overdose, rather than hanging, is the leading cause of suicide among psychiatric patients with physical co-morbidities, particularly using non-psychotropic medications. There is potential for means restriction in preventing suicide among these patients.