| Abstract | This is a systematic review of studies assessing the effects of polychromatic (white) ambient light on mood in healthy adults. We hypothesized that higher melanopic equivalent daylight illuminances (EDI) would be associated with better mood. The search identified 2,994 publications, of which 14 met inclusion criteria. The resulting database included the spectral power distributions, illuminances, mood measures, and methods. We used the CIE S026 toolbox to calculate the five α-opic EDI values to characterize the light exposures in each study. Regression models tested the associations between predictors α-opic EDI, duration, and timing, and the outcome, mood. The results showed that none of the five α-opic values were significantly associated with mood (all estimates <0.044, p > .490). A longer duration of light exposure (all estimates <0.154, p < .018) and timing of light exposure in the morning (all estimates <0.233, p < .001) were associated with better mood, but these effects did not persist after adjusting for the data being nested within studies. Average mood scores remained reasonably consistent across different α-opic EDI profiles, suggesting that exposure profiles might not influence mood. Notably, none of the studies included had an experimental condition with a peak for melanopic EDI greater than the other α-opic EDI values, therefore the hypothesized association between melanopic EDI and mood could not be tested. Future research designs should contrast selected light parameters to identify the photoreceptors involved in the processes of interest. |
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