How ambient temperature affects mood: an ecological momentary assessment study in Switzerland

Abstract

Background Recent research has suggested that an increase in temperature can negatively affect mental health and increase hospitalization for mental illness. It is not clear, however, what factors or mechanisms mediate this association. We aimed to (1) investigate the associations between ambient temperatures and bad daily mood, and (2) identify variables affecting the strength of these associations (modifiers) including the time, the day of the week and the year of the mood rating, socio-demographic characteristics, sleep quality, psychiatric disorders and the personality trait neuroticism in the community. Methods Data stemmed from the second follow-up evaluation of CoLaus|PsyCoLaus, a prospective cohort study conducted in the general population of Lausanne (Switzerland). The 906 participants rated their mood level four times a day during seven days using a cell phone app. Mixed-effects logistic regression was used to determine the association between daily maximum temperature and mood level. Participant ID was inserted as a random effect in the model, whereas the time of the day, the day of the week and the year were inserted as fixed effects. Models were controlled for several confounders (socio-demographic characteristics, sleep quality, weather parameters and air pollutants). Stratified analyses were conducted based on socio-demographic characteristics, sleep quality, presence of psychiatric disorders or a high neuroticism. Results Overall, the probability of having a bad mood for the entire day decreased by 7.0% (OR: 0.93: 95% CI 0.88, 0.99) for each 5 °C increase in maximum temperature. A smaller and less precise effect (-3%; OR: 0.97: 95% CI 0.91, 1.03) was found when controlling for sunshine duration. A higher association was found in participants with bipolar disorder (-23%; OR: 0.77: 95% CI 0.51, 1.17) and in participants with a high neuroticism (-13%; OR: 0.87 95% CI 0.80, 0.95), whereas the association was reversed for participants with anxiety (20%; OR: 1.20: 95% CI 0.90, 1.59), depression (18%; OR: 1.18 95% CI 0.94, 1.48) and schizophrenia (193%; OR: 2.93 95% CI 1.17, 7.73). Conclusions According to our findings, rising temperatures may positively affect mood in the general population. However, individuals with certain psychiatric disorders, such as anxiety, depression, and schizophrenia, may exhibit altered responses to heat, which may explain their increased morbidity when exposed to high temperatures. This suggests that tailored public health policies are required to protect this vulnerable population.

Impact of air pollution and climate change on mental health outcomes: an umbrella review of global evidence

“…In this scenario, we demonstrate here that global warming negatively affects mental health. However, despite the huge magnitude of the problem, the biological mechanisms underlying this association remain unknown and likely involve complex multifactorial relationships [97][98][99] . Some evidence suggests that exposure to hot temperatures may directly affect brain function, with alterations in proper oxygenation and permeability of the blood-brain barrier.…”

Influences of Indoor Air Temperatures on Empathy and Positive Affect

“…Consequently, one could argue that our thermal perception of the environment has a more important role in regulating our psychosocial aspects than actual physical warmth during work, although these effects were very modest. This effect could be due to the fact that people associate higher temperature conditions with the opportunity to go out and be involved in more social activities [ 25 , 53 ]. However, other variables, for example the availability of other people to go out, can further influence the outcomes, suggesting the presence of combined effects, which supports the modest direct effect of the thermal perception on psychosocial variables.…”

“…However, this study did not control for the presence of any mental health difficulties reported in the sample taken into consideration. Recent studies investigating the effect of outdoor ambient temperature on mood suggest that individuals with specific mental health difficulties are more prone to negative affect, and potentially to acts of aggression, than individuals with no mental health difficulties when there is an increase in ambient temperature [ 25 ]. According to Bundo, Preisig, Merikangas, Glaus, Vaucher, Waeber, Marques-Vidal, Strippoli, Müller, and Franco [ 25 ], this could be due to the fact that those people might have less opportunities for social activities, which become more prominent under rising temperatures, a weather state that encourages social activities and social connection.…”

Humid heat environment causes anxiety-like disorder via impairing gut microbiota and bile acid metabolism in mice

“…Previous studies have also shown that extremely high temperature and high humidity can affect emotional and behavioural disorders and increase the number of patients with conditions such as schizophrenia, mania, and neurological disorders 6 . As the problem of global warming further intensifies, the impact of extremely humid heat environments on negative emotions (e.g., anxiety) in humans will increase further, and the impact of environmental changes on mental health has attracted increasing attention 7 , 8 . How climate (e.g., temperature and humidity) changes lead to neuropsychiatric disorders remains largely unknown.…”