Disentangling the effects of daily physical activity and natural white light exposure on affect.

Physical activity has a well-known positive effect on mood and often occurs outside in natural light. The specific effects of natural light exposure on mood are understudied, but clinically significant as it may reflect a widely accessible method to enhance mood. This study thus aimed to disentangle the effects of (a) physical activity and (b) natural light exposure on daily mood. For 2 weeks, 131 participants wore actigraphs that assessed their physical activity and light exposure. Participants also rated their positive and negative affect 3 times/day. Multilevel models separated within-person (relative to self) and between-person (relative to others) effects. Results suggest that within person increases in daily natural light exposure ( = 0.03, < .05) and physical activity ( = 0.08, < .05) were independently associated with increased positive affect, but not negative affect. Results remained significant controlling for between-person effects and other covariates, including overall depression severity. Findings offer preliminary evidence that natural light exposure may be one pathway to increase positive affect in everyday life. (PsycInfo Database Record (c) 2025 APA, all rights reserved).