Abstract
<title>Abstract</title> <p>Background Rising temperatures are associated with increased psychiatric morbidity, although the mechanisms behind this remain poorly understood. This study investigates the role of psychotropic medications in the relationship between ambient heat and urgent psychiatric hospitalisations in a Swiss psychiatric clinic. Methods We applied a case-time series design with distributed lag models to examine the short-term association (0–3 lag) between mean temperature and the risk of urgent hospitalisations using individual-level data from the private psychiatric clinic (2017–2024). We evaluated the role of medications as effect modifiers for all and by sub-diagnosis. Results The risk of urgent psychiatric hospitalisation increased by 20% for each 10-degree rise in daily mean temperature (1.20, 95% Confidence Interval (CI) 1.04; 1.40), with higher risks in patients aged 65 years and older and those aged 30 years and younger (1.56 (1.12–2.16); 1.35 (1.07–1.72)). Regardless of the diagnosis, patients taking antipsychotics (1.18 (1.02–1.23)) and anxiolytics (1.15 (1.05–1.24)) showed higher vulnerability to heat, whereas no effect was found in antidepressants and antipsychotics. Conclusion Our results confirm that psychiatric patients are vulnerable to increasing temperatures, and this risk may be modulated by psychotropic medication use. This research contributes to a better understanding of the mechanisms behind the heat sensitivity of certain mental health conditions and supports the development of targeted public health measures.</p>