A new study suggests that people with depression may have an altered response to sunlight, which could reduce its positive effects on mood. Using wrist-worn activity sensors, researchers monitored participants’ sunlight exposure and physical activity over two weeks. They found that individuals with depression had lower levels of physical activity, especially on days with shorter amounts of sunlight, compared with people without depression.
Throughout the year, the seasons change, bringing visible changes to nature, such as the falling leaves in the yard, which are often left unpicked.
While winter is marked by celebrations like Christmas, which bring moments of joy and affection, the prolonged absence of sunlight can cause some people to feel unexplained sadness and melancholy.
Globally, the prevalence of major depressive disorder (MDD) and bipolar disorder (BD) has recently reached over 350 million and 60 million people, respectively, affecting over 5% of the world’s population and imposing a significant disease burden.
A significant proportion of these individuals (10–30%) experience variations in important psychosocial domains such as motivation, sleep, and mood, influenced by seasonal patterns of recurrent episodes of (hypo)mania and depression.
The subtypes of MDD and BD that are sensitive to these seasonal variations, first described as Seasonal Affective Disorder in 1984, can now be diagnosed using the seasonal pattern specifier in DSM-5 and ICD-11.
This advancement is crucial, as understanding how seasonal changes affect energy and mood can significantly improve self-awareness and help individuals with MDD and BD better manage these disorders.
A recent exploratory study investigated the relationship between sunlight exposure and physical activity in people with depression using the open-source “Depresjon” dataset. Kovtun and Rosenthal conducted a quantitative analysis to examine the link between sunlight and physical activity patterns, seeking to understand the environmental factors that influence seasonality in depressive and bipolar disorders.
Using activity sensors, 23 individuals with unipolar or bipolar depression and 32 healthy controls, recruited from the University of Bergen, were monitored for two weeks.
The data revealed that daily sunlight exposure and photoperiod were directly related to physical activity, as published in PLOS Mental Health on September 25, 2024.
The results showed that depressive states were associated with lower daytime physical activity, while activity increased with greater sunlight exposure. There were also indications that the impact of sunlight on physical activity varied between depressed and non-depressed individuals, suggesting a possible alteration in the physiological response to sunlight in the former.
The Figure shows the relationship between sunlight measures and daily activity. Regression model fits plots are shown for solar insolation versus physical activity (a), photoperiod versus physical activity (b), change in solar insolation from the previous day versus physical activity (c), and solar insolation versus physical activity for insolation <102 W/m2/day (d). Blue objects correspond to healthy study participants, and orange objects correspond to depressed individuals. N = 770 total data points derived from 23 depressed individuals and 32 healthy controls. https://doi.org/10.1371/journal.pmen.0000124.g003
Furthermore, it was hypothesized that increased sedentary behavior among depressed individuals may limit their sun exposure, preventing them from reaping the benefits of sunlight.
The study offers a promising strategy for analyzing the complex interplay between sunlight, physical activity, and depressive states using open-source digital tools.
The researchers highlight that the use of digital biomarkers, such as movement patterns, can contribute to more personalized and predictive diagnoses in mental health.
Integrating objective data on sunlight exposure, collected by NASA satellites or measured by wearable devices, can increase the accuracy of these tools, creating personalized models for individuals susceptible to seasonal mood disorders.
Kovtun and Rosenthal hope that the study will motivate the development of new technologies to support both clinicians and patients in managing the symptoms associated with seasonal mood disorders.
READ MORE:
Seasonality in mood disorders: Probing association of accelerometer-derived physical activity with daylength and solar insolation
Oleg Kovtun and Sandra J. Rosenthal
Plos one mental health, September 25, 2024
Abstract:
Mood disorders are the leading cause of disability worldwide. Up to 30 percent of individuals with major depressive disorder (MDD) and bipolar disorder (BD) display a seasonal pattern of onset, a phenomenon now recognized in the official diagnostic manuals (DSM-5 and ICD-11). Very little is known about the influence of day length (photoperiod) and sunlight intensity (solar insolation) on seasonal patterns in MDD and BD. Here we report a quantitative approach to examine the relationship between sunlight measures and objectively measured motor activity patterns to understand environmental factors driving seasonality in MDD and BD. Our generalized linear model (GLM) assessment of the Depresjon dataset, which includes short-term (up to two weeks) motor activity recordings of 23 unipolar and bipolar depressed patients and 32 healthy controls recruited to the study at the University of Bergen Norway (60.4° N latitude, 5.3° E longitude), revealed significant association of accelerometer-derived daytime physical activity with participant’s depressed state (p<0.001), photoperiod (p<0.001), and solar insolation (p<0.001). Our study presents a generalizable strategy to decipher the complex interplay between sunlight, physical activity, and depressed state using open-source digital tools. The ability to identify mood disturbances, particularly in seasonally susceptible individuals, using passive digital biomarker data offers great promise in informing next-generation predictive, personalized diagnostics in mental health.
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