Objectives To examine the numbers and patterns of patients presenting to an urban acute general hospital with acute mental health presentations and to further investigate any variation related to the COVID-19 pandemic.

Design Retrospective observational cohort study.

Setting An urban acute general hospital in London, UK, comprising of five sites and two emergency departments. The hospital provides tertiary level general acute care but is not an acute mental health services provider. There is an inpatient liaison psychiatry service.

Participants 358 131 patients attended the emergency departments of our acute general hospital during the study period. Of these, 14 871 patients attended with an acute mental health presentation. A further 14 947 patients attending with a physical illness were also noted to have a concurrent recorded mental health diagnosis.

Results Large numbers of patients present to our acute general hospital with mental health illness even though the organisation does not provide mental health services other than inpatient liaison psychiatry. There was some variation in the numbers and patterns of presentations related to the COVID-19 pandemic. Patient numbers reduced to a mean of 9.13 (SD 3.38) patients presenting per day during the first ‘lockdown’ compared with 10.75 (SD 1.96) patients per day in an earlier matched time period (t=3.80, p<0.01). Acute mental health presentations following the third lockdown increased to a mean of 13.84 a day.

Conclusions Large numbers of patients present to our acute general hospital with mental health illness. This suggests a need for appropriate resource, staffing and training to address the needs of these patients in a non-mental health provider organisation and subsequent appropriate transfer for timely treatment. The COVID-19 pandemic and the resulting lockdowns have resulted in variation in the numbers and patterns of patients presenting with acute mental health illness but these presentations are not new. Considerable work is still needed to provide integrated care which addresses the physical and mental healthcare needs of patients presenting to acute and general hospitals.