A study found that awareness and research in circadian dysfunction in bipolar disorder (BD) is needed, as exposure to solar insolation may affect polarity. These findings were published in the Journal of Psychosomatic Research.

Patients (N=7488) with BD I were evaluated for this study between 2010 and 2016 and 2019 and 2021 at 75 sites in 42 countries. Solar insolation at the time of the first BD episode was related with polarity of the episode.

The onset locations had mean monthly minimum to maximum insolation ratios ranging from 0.8370 (Mataram, Indonesia) to 0.0116 (Trondheim, Norway).


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The study cohort comprised 58.3% women, the mean age of onset was 25.5 (SD, 10.5) years, 50.0% had manic or hypomanic polarity at their first BD episode, 52.3% had a family history of a mood disorder, 64.3% had a history of psychosis, and 23.4% had comorbid anxiety, panic, or obsessive-compulsive disorder.

Significant predictors of the polarity of the first BD episode were the ratio of monthly minimum and maximum insolation (b, -1.109; P <.001), gender (b, 0.338; P <.001), and the proportion of the country’s gross domestic product (GDP) spent on health care (b, 0.075; P <.001).

The best fit model predicted that the likelihood of first-episode depression decreased by 6.7% for every 0.1 increase in the ratio of monthly insolation. Odds of having first-episode depression was lowest at the equator. The likelihood of depression was positively related with health care expenditure, in which for every 1% increase in expenditure as a percentage of GDP increased, the odds of depression increased by 7%.

This study was limited by not completing a seasonal analysis.

The study authors concluded, “In patients with BD I, increasing change in solar insolation during the year, between winter and summer or tropical wet and dry seasons, was associated with a first episode with a polarity of depression. Physicians who practice in locations with a large change in solar insolation across the year should monitor even more carefully for BD. Increased awareness and research into the role of circadian dysfunction throughout the course of BD is needed.”

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.

Reference

Bauer M, Glenn T, Achtyes ED, et al. Association between polarity of first episode and solar insolation in bipolar I disorder. J Psychosom Res. 2022;110982. doi:10.1016/j.jpsychores.2022.110982