The Efficacy of Light Therapy in the Treatment of Seasonal Affective Disorder: A Meta-Analysis of Randomized Controlled Trials

Oct 2, 2019Psychotherapy and psychosomatics

How Well Light Therapy Works for Seasonal Depression: A Review of Controlled Studies

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Abstract

Bright light therapy (BLT) showed a standardized mean difference of -0.37 in depression ratings compared to placebo.

BLT demonstrated a significant reduction in depression scores among adults with seasonal affective disorder (SAD).
The treatment was associated with a response rate risk ratio of 1.42, indicating a higher likelihood of improvement compared to placebo.
Nineteen studies were included, highlighting the variability in study design and quality.
Moderate heterogeneity among the studies was observed, along with a moderate-to-high risk of bias.
The findings suggest that while BLT is effective, further large-scale, high-quality trials are needed to confirm its efficacy.

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BACKGROUND: Bright light therapy (BLT) has been used as a treatment for seasonal affective disorder (SAD) for over 30 years. This meta-analysis was aimed to assess the efficacy of BLT in the treatment of SAD in adults.

METHOD: We performed a systematic literature search including randomized, single- or double-blind clinical trials investigating BLT (≥1,000 lx, light box or light visor) against dim light (≤400 lx) or sham/low-density negative ion generators as placebo. Only first-period data were used from crossover trials. The primary outcome was the post-treatment depression score measured by validated scales, and the secondary outcome was the rate of response to treatment.

RESULTS: A total of 19 studies finally met our predefined inclusion criteria. BLT was superior over placebo with a standardized mean difference of -0.37 (95% CI: -0.63 to -0.12) for depression ratings (18 studies, 610 patients) and a risk ratio of 1.42 (95% CI: 1.08-1.85) for response to active treatment (16 studies, 559 patients). We found no evidence for a publication bias, but moderate heterogeneity of the studies and a moderate-to-high risk of bias.

CONCLUSIONS: BLT can be regarded as an effective treatment for SAD, but the available evidence stems from methodologically heterogeneous studies with small-to-medium sample sizes, necessitating larger high-quality clinical trials.

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The Efficacy of Light Therapy in the Treatment of Seasonal Affective Disorder: A Meta-Analysis of Randomized Controlled Trials

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