Unintentional drug-related deaths in people with mental illness in NSW Australia, 2012-2016: a retrospective cohort study

Purpose People with mental illness are a vulnerable and stigmatised group with poor health outcomes including greater premature mortality. This study aimed to investigate trends and rates of change in unintentional drug-related deaths for people with mental illness, describe types of medicines involved, and identify populations at risk in a cohort from New South Wales, Australia. Methods Features of unintentional drug-related deaths for people with mental illness between 2012 and 2016 were identified in a retrospective review of data from the National Coronial Information System. Results A total of 495 unintentional drug-related deaths were identified (1.6 deaths/100,000 population), showing an upward trend (p < 0.01). The most common substance involved was diazepam in both genders (males 135/319, 42%, female 76/176, 43%) and more than one contributory drug was included in 80% of cases. Between 2012 and 2016, amphetamine-related deaths showed the highest increase (3.2-fold), followed by codeine (2.5-fold) and quetiapine (2.5-fold). Males (RR 1.8, 95% CI 1.5-2.2) and people aged 35-44 (RR 1.7, CI 1.3-2.2) were more likely to die from unintentional drug-related deaths compared with the reference (females and people aged 25-34). Conclusion This study found that the drugs commonly involved in deaths are also the drugs commonly used by and prescribed to people with mental illness. There were also significant differences between gender, age group, and marital status in the trend and rate of unintentional drug-related deaths for people with mental illness. A multifaceted approach encompassing both pharmaceutical prescribing and targeted public health messaging is required to inform intervention and prevention strategies.