Almost one in five emergency department presentations are by mental health clients: a secondary data analysis.

Aim: Mental health-related emergency department (ED) presentations are steadily increasing, including presentations for both mental health and non-mental health concerns by existing clients of mental health services. The study aim was to examine and compare mental health clients and non-clients' ED presentations, identify data and clinical gaps and make recommendations for improvement.

Method: De-identified 2017/2018 ED data were used to describe presentations for current and recent (within last 5 years) clients of specialist public mental health and addiction services, compared to presentations of non-mental health clients.

Results: Of 49,170 presentations, 18% were by clients of mental health services. Compared to other ED presenters, mental health clients were often younger, female and Māori, required more urgent care and waited longer. Mental health-related International Classification of Diseases (ICD) codes/referrals were most common for presentations by current mental health clients, whereas pain and trauma were often the reason for prior mental health clients' presentations. Discharge diagnoses rarely included self-harm behaviour, and admissions for these clients were more commonly by ED rather than mental health services.

Conclusion: Mental health clients are common in ED. Enhanced mental health data capture and improved systems and processes are needed to ensure that ED staff can better meet their often-complex needs.