Indoor sunlight improves health in hospitals, schools, and workplaces, and there is clinical evidence for the impact on depression. But the impact of indoor sunlight on residents’ health and well-being in domestic dwellings is unclear. Understanding this relationship could have important implications for building design and residents’ indoor behavior, and impacts on health. Using a cross-sectional survey, we investigated the relationship between annual indoor sunlight opportunity and psychological well-being in 40 residents of high-rise dwellings in a socioeconomically deprived area in Glasgow, Scotland.

Perceived physical health, physical activity, psychological distress,
and indoor environmental factors were potential mediators of
the relationship between annual sunlight opportunity and wellbeing.
We used novel simulation modeling of window size, orientation,
occlusion, and occupant behavior to measure annual sunlight
opportunity.

We found a significant positive association between well-being
and annual indoor sunlight opportunity but no relationship between
sunlight and objective indoor environmental variables, including air
quality, bacteria, and fungi. Our sample had generally poor physical
and mental health. Perceived physical health, lower psychological
distress, more physical activity, and better perceived environmental
quality were associated with greater psychological well-being. Perceived physical health mediated the impact of sunlight on well-being. Findings merit replication in larger and more diverse samples but have important implications for building design and advice to residents on window occlusion.