Seasonal Affective Disorder is familiar to many of our readers; as the planet turns, days get shorter and nights get longer. In California, cloudy and rainy weather takes over from the sunshine that we’re used to, and many people get the “blues”. Others encounter more serious dysfunction, and may require medical intervention to cope.
Seasonal changes affect our circadian rhythms, and require adjustments throughout the year, as temperature warms or cools, days lengthen or shorten and rainy and dry weather alternates according to climate zone. However, now people are noticing more variation in age-old patterns as industrialization, pollution, and climate change begin to bite.
New research coming out considers changing seasonal patterns due to human interactions with the environment, and how this affects individuals’ circadian rhythms. We now have entirely new seasons: “fire season”, “smog season”, “wind season”, and so forth, and some places are even losing seasons, as less and less snow falls in areas that previously had snowy winters. Will these changes have an effect on people suffering from bipolar disorder and unipolar depression?
Clinicians are beginning to encounter, and find ways to measure, climate anxiety, which disproportionately affects those who are already vulnerable to seasonal changes in their mood or functioning. Patients who have noticed the onset of deeper depression in winter time, for example, may now have their depression exacerbated by anxiety about how much worse conditions may get in the future. Bipolar patients whose mood swings are partly conditioned by seasonal changes may fear additional problems resulting from changes in the very seasonal patterns that they are learning to compensate for.
Moreover, some of the seasonal changes may have health effects of their own. Intense heat and heat waves can cause or worsen a number of medical conditions, including depression and anxiety. Increased air pollution and smog, which is often related to seasonal weather patterns, also causes respiratory and other health problems.
Researchers are calling for clinicians to consider the importance of seasonal factors in treatment planning and the need for targeted interventions to address climate-related anxiety in mood disorder patients.
References:
Mohamed, S.M., Elbeh, K., Mohammed, N.A.E. et al. Seasonal patterns and climate change anxiety in mood disorders: a comparative study of bipolar disorder and depression. Middle East Curr Psychiatry 32, 26 (2025). https://doi.org/10.1186/s43045-025-00518-w
Smith, T. E. L., & Liu, F. H. M. (2025). Seasons and the Anthropocene. Progress in Environmental Geography, 4(3), 342-362. https://doi.org/10.1177/27539687251348470 (Original work published 2025)