Effects of light therapy on depression, anxiety and sleep quality in mental disorders: A systematic review and...

Light therapy (LT) has become a frequently used treatment method for treating emotional disturbance (depression and anxiety) and sleep disorders due to its convenience, safety and low cost. Previous studies discovered that light, sleep and mood are closely related.

The whole process followed PRISMA 2020, all studies were searched in 5 databases from January 1st 2020 to June 30th 2025. The quality of studies was assessed by Risk of Bias Tool 2 and GRADE. The primary outcome was depression improvement, and secondary outcomes were anxiety improvement and sleep quality. Heterogeneity was assessed by I² statistics. Subgroup analysis and meta-regression analysis were conducted to explore possible influencing factors. Sensitivity analysis was used to evaluate robustness.

Depression improvement between two groups in patients with non-seasonal MDD or StD both reached a significant level (SMD = 0.35, 95% CI [0.11, 0.60], p = 0.0, I² = 19.04%; SMD = 0.86, 95% CI [0.51, 1.21], p = 0.00, I² = 68.49%, respectively). LT duration, illuminance, disease subtypes, and medication status were significantly influenced the effect of LT (β = 0.13, p = 0.02; β = -0.33, p = 0.04; β = -0.001, p = 0.02; β = -0.49, p = 0.02, respectively). LT also had a positive effect on anxiety, subjective sleep quality and daytime sleepiness.

LT had a positive effect on depression, anxiety and subjective sleep quality. LT duration, illuminance, disease subtype and medication status might be significant influencing factors.