Light therapy for preventing seasonal affective disorder.

Study answer

What this study found

Light therapy reduced winter SAD incidence numerically versus no light therapy in this small RCT, but confidence intervals were wide and the evidence quality is very low. No adverse events were reported. There is no comparative evidence versus other preventive options. Conclusion: efficacy and safety remain uncertain; decisions should be guided by patient preferences; more high-quality trials are needed.

Study & population

Single-centre, randomized, non-blinded controlled trial conducted in the Netherlands; 46 adults with a history of SAD who were non-depressed at baseline; outpatient setting; three-arm design: bright white visor light, infrared visor light, and no light exposure.

Intervention

Bright white visor light: 2500 lux, 30 minutes daily in the morning (6:00–9:00), at home, during October–April across two winters (1993–1994 and 1994–1995).

Key limitation

Small sample size; single study; high risk of bias (unblinded, incomplete data, self-rated outcomes); no adverse event data; limited participant characteristic reporting; older visor-light intervention with limited generalizability; very wide confidence intervals.

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Original abstract