Light Therapy for Older People with Depressive Symptoms: Systematic Review and Meta-Analysis

Background/Objectives: Light therapy has emerged as a promising non-pharmacological treatment for depressive symptoms. This meta-analysis aims to evaluate the effectiveness of light therapy specifically for depressive symptoms in elderly populations, with a focus on how different light intensities and spectra influence treatment outcomes. Methods: A systematic search targeting studies on light therapy for depressive symptoms in older adults was performed across multiple databases, including PubMed, Google Scholar, PsycINFO, and EMBASE, covering studies from database inception until July 2024. A total of 565 records were identified, with 461 studies remaining after removing duplicates. Following the screening of titles and abstracts, 54 studies underwent full-text review, resulting in the inclusion of 22 studies with a total of 1290 participants (687 in the intervention group and 603 in the control group). Results: The overall effect size for light therapy on depressive symptoms was moderate (Hedges' g = 0.525, p < 0.001). Higher light intensities (10,000 lux and above) demonstrated significantly greater effectiveness compared to lower intensities. White light had the most substantial effect, while bluish light showed moderate efficacy. Significant heterogeneity was observed across studies (I² = 80.459%), indicating variability in treatment outcomes based on study design, intensity, and light spectrum. Conclusions: This meta-analysis confirms that light therapy is an effective treatment for reducing depressive symptoms in older adults, particularly at higher intensities and with specific light spectra such as white light. Given the heterogeneity in results, future research should focus on optimizing treatment parameters to enhance clinical outcomes within this population.