The Effect of Light on Wellbeing: A Systematic Review and Meta-analysis

Background: Due to the dominant presence of studies and reviews exploring the impact of light on physical and mental illness, studies specifically investigating the effect of light on wellbeing are often overshadowed. The aim of this review is to give an overview of specifically these studies conducted on light and wellbeing, and to summarize the reported effects. Methods: After a literature search in Pubmed, PsychInfo, and Web of Science, 74 studies were found eligible to be included in this systematic review, i.e. they included surveys assessing wellbeing, happiness, life satisfaction, positive affect, or quality of life. Of these 74 studies, 30 were included in the meta-analysis and assessed for their risk of bias. Results: The meta-analysis showed a pooled effect size of 0.47 (CI = 0.31 – 0.63), indicating that light has a small-to-moderate positive effect on wellbeing. The heterogeneity between the studies was high (I2 = 96.12%). After removing outliers and studies with a high risk of bias, the sensitivity analysis showed the pooled effect size to be robust (0.51, CI = 0.32 – 0.70). Conclusion: Although the sensitivity analysis indicated a robust effect, the results might still be biased due to the relatively small sample sizes of the included studies, risk of bias in the designs (due to e.g. difficulties dealing with confounders and the reporting of the outcomes), and publication bias. We encourage future studies to try to replicate these positive results in larger samples, and to give extensive details about the light design and statistical outcomes, to increase the number of studies that can be included in these types of systematic reviews.