Heatwaves may increase aggressive patient behaviour on mental health wards, according to the first study of its kind, published today in the Royal College of Psychiatrists' BJPsych Open journal.
The researchers from ZfP Südwürttemberg and Ulm University in Germany looked at local weather data and incident reporting data to examine the impact of hot weather on mental health inpatient wards.
They found that there were on average 15% more aggressive incidents on days over 30°C (9.7 per day) compared to days under 30°C (8.4 per day).
They also found a clear relationship between the temperature of hot days (those over 30°C) and the number of aggressive incidents. The hotter the weather, the higher the rate of incidents, reaching a peak of 11.1 on the very hottest days (over 33.5°C).
This suggests that temperature is the cause of the increase in incidents, rather than another factor. They found no equivalent correlation between temperature on hot days and the use of restrictive practices by hospital staff.
Staff recorded aggressive incidents using a standardised protocol, documenting the nature of the aggression (e.g. physical, verbal), the target (e.g. staff, patients), the impact and any subsequent measures taken.
The data came from six German mental health hospitals and covered 13 years (2007-2019), 1,007 beds and 164,435 admissions. Over this period, there were a total of 207 days over 30°C. All six hospitals were built in line with modern building standards, but none had air-conditioning.
Dr Hans Knoblauch, lead author of the study, said: "The climate emergency means that many areas of the world could experience significantly more hot weather in the future.
"While more research into the mental health consequences is needed, these findings could have practical implications for mental healthcare, particularly around hospital design and architecture."
His colleague, Professor Tilman Steinert, from Ulm University, said: "These findings highlight an underappreciated impact of the climate emergency on mental health services. Increased aggression is an indicator of increased distress and an environment that is failing to help patients recover.
"Urgent action is now needed, to replicate the findings of this study using more measurements within mental health hospitals, to invest in those hospitals, and to tackle the climate crisis. Mental health patients deserve better."