A controlled comparison of light box and head-mounted units in the treatment of seasonal depression

Abstract

Background: Patterns of response to the light box and head-mounted unit (HMUs) in seasonal affective disorder (SAD) appear to differ. The current study employed a "no light" condition to compare the response rates with the light box and HMU against a plausible placebo.

Method: Forty-three subjects with DSM-III-R nonpsychotic, unipolar major depression, seasonal subtype, were randomly assigned, in a double-blind manner, to receive 2 weeks of active treatment with a light box (N=9) or HMU (N=12) that emitted no visible light, or 2 weeks of placebo treatment with a light box (N=12) or HMU (N=10) that emitted no visible light. Response was defined as a 50% or greater reduction in both the 17-item "typical" score and 8-item "atypical" score on the Structured Interview Guide for the Hamilton Rating Scale for Depression-SAD version (SIGH-SAD).

Results: Using ANOVA for repeated measures, with change in total SIGH-SAD score as the dependent measure, we found no significant main effect of light (F=0.20, p=N.S.) or unit (F=0.50, p=N.S.), and no interaction (F=0.21, p=N.S.). Using log-linear analysis, we found no significant difference in response rate between the four cells (likelihood ratio chi-square = 2.1, p=N.S.). Using chi-square analysis, we found no significant difference in response rates between patients who received light (48%) versus patients who received no light (41%; chi-square = 0.2, p=N.S.) or between patients who received the light box (38%) versus HMU (50%; chi-square = 0.62, p=N.S.).

Conclusion: The failure to detect any significant difference in efficacy between active and placebo treatments calls into question the specificity of light in light therapy for SAD. Methodological limitations, particularly small sample size, are discussed.