The duration of light treatment and therapy outcome in seasonal affective disorder

AbstractBackgroundSeasonal affective disorder (SAD) is characterized by recurrent episodes of major depression with a seasonal pattern, treated with light therapy (LT). Duration of light therapy differs. This study investigates retrospectively whether a single week of LT is as effective as two weeks, whether males and females respond differently, and whether there is an effect of expectations as assessed before treatment.Methods83 women, and 25 men received either one-week (n=42) or two weeks (n=66) of LT were included in three studies. Before LT, patients׳ expectations on therapy response were assessed.ResultsDepression severity was similar in both groups before treatment (F(1,106)=0.19ns) and decreased significantly during treatment (main effect “time” F(2,105)=176.7, p