Effectiveness of visible light for seasonal affective disorder: A systematic review and network meta-analysis

To determine the efficacy of different visible light therapies in treating seasonal affective disorder (SAD) through both direct and indirect comparisons.

We conducted a search of the PubMed, Embase, Cochrane Library, Scopus, Web of Science, China National Knowledge Infrastructure, Wanfang, VIP, and China Biomedical Literature databases for randomized controlled trials up to November 12, 2024. The using search terms were: white light, blue light, green light, and SAD/winter depression. Two independent researchers reviewed and extracted the data.

After screening, a total of 17 studies were obtained, involving 773 patients. These studies included 14 on white light, 6 on blue light, 2 on green light, and 5 on red light. The results indicated that, in terms of alleviating seasonal mood dysregulation or typical depressive symptoms, white light therapy was most effective, followed by green light, blue light and red light. Furthermore, usual care of SAD was found to be more effective than green light therapy in improving seasonal mood dysregulation.

The existing evidence suggests that white light may be the best visible light therapy for patients with SAD, with usual care being more effective than green light. However, larger-scale studies are still needed to verify the potential differences among green light and blue light, further comprehensively evaluate the effectiveness of visible light at different wavelengths for SAD.