Seasonal Variation in Mood and Associated Patterns of Sleep, Activity, Circadian Rhythms and Light
Year: 2026
Type: article
Study design: Observational Study
Abstract: ABSTRACT Background Mood symptoms vary seasonally, yet the underlying mechanisms remain unclear. We tested whether wearable-derived sleep, activity, circadian, and light exposure patterns mediate seasonal effects on mood in youth with emerging mood disorders. Methods We analysed 733 observation periods from 422 Australian youth (mean age 24.3±5.5 years; 63% female) attending early-intervention mental health services. Each observation comprised a clinical assessment paired with ≥5 valid days of GENEActiv wrist actigraphy. Season was modelled using sine-cosine functions of day-of-year. Sleep, activity, and circadian features were reduced using Joint and Individual Variation Explained, and light exposure features were reduced via principal components analysis. Linear mixed-effects models tested seasonal effects on depressive, psychiatric, manic, and functional outcomes. Mediation was examined using Sobel screening followed by cluster bootstrapping (1,000 iterations). Results Depressive (β=−0.67, p=0.023) and negative symptoms (β=−0.17, p=0.041) peaked in winter, whereas manic symptoms peaked in autumn (β=0.24, p=0.018). Reduced day-to-day variability in moderate-to-bright ambient light exposure (fewer transitions to brighter environments) mediated winter increases in depressive (indirect β=−0.06, p=0.006) and negative symptoms (indirect β=−0.05, p<0.001). Higher activity levels partially mediated season’s effect on depressive symptoms (indirect β=−0.010, p=0.032). Extended sleep with nocturnal activity mediated season’s effect on negative symptoms (indirect β=−0.02, p=0.001). No mediators emerged for manic symptoms. Conclusions Light exposure variability—reflecting constrained engagement with brighter environments during winter—emerged as the dominant mediator of seasonal mood worsening in Australian youth, with smaller contributions from sleep-activity-circadian patterns. These findings identify daily light variability as a promising, modifiable target for intervention.
Source: Journal of Biological Rhythms
Authors: Mirim Shin, Emiliana Tonini, Joanne S Carpenter, Mathew Varidel, Alissa Nichles, Natalia Zmicerevska, Elizabeth Phung, Connie Janiszewski, Minji Park, Daniel Froggatt, Dhyana Hanlon, Amira Chami, Min K Chong, Haley M LaMonica, Frank Iorfino, Angus C Burns, Sean W Cain, Sun Jung Kang, Vadim Zipunnikov, Wei Guo, Debangan Dey, Andrew Leroux, Kathleen R Merikangas, Elizabeth M Scott, Ian B Hickie, Jacob J Crouse
Language: English
Subfield: Endocrine and Autonomic Systems
Field: Neuroscience
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $4,400
OpenAlex ID: W7160266360