Outside temperatures are associated with ambulance calls due to psychiatric emergencies. A retrospective chart survey

Prior data indicate that extreme weather conditions may acutely exacerbate psychiatric diseases, but it is unclear if this affects Emergency Medical Services (EMS). We reviewed all EMS missions involving suspected psychiatric conditions in Vienna, Austria, between 2018 and 2023. We calculated Poisson regression models with the number of psychiatric calls per day as the dependent variable and outdoor apparent temperature (AT) as the independent variable. In sensitivity analyses, we controlled for seasons and daylight duration, and we present call rate dynamics. High AT was associated with an increase in psychiatric emergency calls (+4%, 95% CI [2; 5]; p<0.001). This effect remained significant after controlling for seasons but faded after including the duration of daylight. Fewer missions were encountered during cold AT (-7%, 95% CI [-8; -6]; p<0.001) and snow (-12%, 95% CI [-15; -9]; p<0.001), an effect that was consistent throughout all models. Higher outdoor temperatures tend to be associated with higher numbers of EMS missions due to psychiatric emergencies. Cold weather and snow seem to be associated with fewer missions. Strategies to mitigate the impact of heat on an excessive rate of respective EMS activations could include warning systems and prevention measures.