How ambient temperature affects mood: an Ecological Momentary Assessment study in Switzerland

Abstract

BACKGROUND AND AIM: Recent studies indicate that increasing temperatures could negatively affect mental health and lead to increased psychiatric hospitalizations. However, evidence on the potential mechanisms mediating this association is limited. Mood can act as a potential mediator. We aimed to investigate the short-term association between ambient temperature and daily mood in a cohort population in Lausanne, Switzerland. METHODS: Participants from CoLaus|PsyCoLaus who completed the Ecological Momentary Assessment (2015-2017) were included. Data on several mood markers were collected four times daily through a cellphone. A principal component analysis was conducted to create an aggregate index of average daily mood (transformed into a binary variable indicating the presence of positive or negative mood). The effect of daily mean temperature (DMT) on mood was assessed using a mixed-effects model, and it was controlled for sleep, day of the week, season, sunshine duration and humidity. Stratified analyses were conducted by age, sex, and presence of major depressive disorder (MDD) or generalized anxiety disorder (GAD). RESULTS:The study included a total of 946 participants. Overall, probability of having good mood increased by 2.4% (95%CI 0%, 4.5%) for each 1°C increase in DMT, instead increasing temperatures was associated with bad mood in participants with MDD (7.1%; 95%CI, -21.2%, 6.4%) and GAD (-5.7%; 95%CI -49.2%, 26.4%). Larger association estimates were found in males (4.8%; 95%CI 1.4%, 8.0%, vs 1.1%; 95%CI, -2.3%, 4.4% in females), while similar estimates were found for all age categories. CONCLUSIONS:Our preliminary findings suggest that increasing temperatures could positively affect mood in the general population. This association seems to be reversed in individuals suffering from mental disorders, thus suggesting a possible explanation for the increased morbidity in psychiatric patients during heat exposure. This finding supports the need for specific public health policies to protect this vulnerable population from the consequences of a changing climate. KEYWORDS: climate change, temperature, mood, mental health, psychiatric disorders, Ecological Momentary Assessment