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TOPLINE: 

Each 1°C increase in the mean daily temperature reduced the symptoms of depression by 0.2% but increased the symptoms of mania by 0.4% in patients with mood disorders, new research showed.

METHODOLOGY:

• Researchers analysed data from 4000 adults (mean age, 30.9 years) with depressive symptoms and 2132 adults (mean age, 30.4 years) with manic symptoms, collected between 2021 and 2023 through the smartphone application juli.
• Patient Health Questionnaire-8 (PHQ-8) and Altman Self-Rating Mania Scale (ASRM) scores, used to measure depressive and manic symptoms, respectively, were obtained.
• In the 2 weeks before completing the PHQ-8 or ASRM assessment, real-time ambient temperature data were obtained using participant smartphone geolocations.
• The analysis was adjusted for demographic and weather variables, including sex, humidity, sunshine, and air pollution, and stratified by season.

TAKEAWAY:

• Each 1°C increase in mean daily temperature was associated with a 0.2% reduction in depressive symptoms (coefficient, 0.998; 95% CI, 0.997-0.999) and a 0.4% increase in manic symptoms (coefficient, 1.004; 95% CI, 1.001-1.007).
• Spring showed the strongest association with depressive symptoms, with each 1°C increase corresponding to a 0.5% reduction in depressive symptom scores (coefficient, 0.995; 95% CI, 0.992-0.999).
• Autumn had the most pronounced effect on manic symptoms, with each 1°C increase associated with a 1.1% increase in manic symptom scores (coefficient, 1.011; 95% CI, 1.002-1.021).
• Individual temperature norms influenced the association between temperature and symptoms, suggesting that departure from usual temperature exposure may be more important than absolute temperature values.

IN PRACTICE:

"This study suggests it is important for people living with bipolar disorder, mental health professionals, and public mental health bodies to be aware of the impact of extreme heat events on people living with bipolar disorder," the authors wrote. "Understanding the effect of temperature on symptoms before reaching more severe outcomes of hospitalisation or crisis is invaluable for mental health services preparedness and targeted mental health support and interventions," they added.

SOURCE:

The study was led by P. Clery, University College London, London, United Kingdom. It was published online on March 11 in the Journal of Affective Disorders.

LIMITATIONS:

The limitations included restricted geographical and exposure data due to privacy regulations, and potentially inaccurate heat exposure estimates. The sample was non-random and predominantly comprised younger, female participants with smartphone access, potentially limiting generalisability. Seasonal variations in application usage may have influenced symptom reporting. Incomplete and potentially inaccurate data on confounders such as age, race, socioeconomic factors, medication use, comorbidities, and lifestyle factors may have limited the analysis and influenced the findings.

DISCLOSURES:

Several authors reported receiving funding and research grants from various sources. Details are provided in the original article. Two authors reported receiving consultancy fees from juli Health, and one of them reported being a co-founder of juli Health.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.