Digital biomarkers shedding light on seasonality in mood disorders. Up to 30 percent of individuals with major depressive disorder and bipolar disorder display a seasonal pattern of symptoms. Physical activity is linked to depressed state, daylength and sunlight intensity

In their new study, Kovtun and Rosenthal used a quantitative approach to examine the relationship between sunlight measures and objectively measured movement activity patterns to begin to understand the environmental factors driving seasonality in major depressive disorder and bipolar disorder. They used motor-activity recordings collected via accelerometers (which measure the rate of change of the velocity of an object with respect to time) from 23 individuals with unipolar or bipolar depression and 32 individuals without depression. Participants were recruited at the University of Bergen, Norway.

The findings revealed relationships between daytime physical activity, depressed state, photoperiod and solar insolation. In particular, more depressed states were associated with lower daytime activity, whilst daytime activity increased with photoperiod and solar insolation. Additional results suggest that the impact of solar insolation on physical activity may differ between depressed individuals and those who are not. This finding could indicate that depressed individuals exhibit an altered physiological link between energy input (i.e., solar insolation) and physical activity. On the other hand, it is also possible that increased sedentary behavior results in reduced time spent outdoors and does not allow depressed people to capitalize on the benefits of sunlight exposure.

[https://www.news-medical.net/news/20240925/Wrist-based-sensors-provide-insights-into-sunlighte28099s-impact-on-depression.aspx](https://www.news-medical.net/news/20240925/Wrist-based-sensors-provide-insights-into-sunlighte28099s-impact-on-depression.aspx)