title: The duration of light treatment and therapy outcome in seasonal affective disorder.
abstract: BACKGROUND
  Seasonal 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.
  
  
  METHODS
  83 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.
  
  
  RESULTS
  Depression 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<0.001). The speed of therapy response differs significantly in treatment duration, in favor of 1 week (F(2,105)=3.2, p=0.046). A significant positive correlation between expectations and therapy response was found in women (ρ=0.243, p=0.027) and not in men (ρ=-0.154,ns). When expectation was added as a covariate in the repeated-measures analysis it shows a positive effect of the level of expectation on the speed of therapy response (F(2,104)=4.1, p=0.018).
  
  
  CONCLUSIONS
  A limitation is the retrospective design.
  
  
  CONCLUSIONS
  There is no difference between 1 and 2 weeks of LT in overall therapy outcome, but the speed of therapy response differed between 1 week LT and 2 weeks LT. Together with the significant correlation between expectations and therapy response in women, we hypothesize that expectations play a role in the speed of therapy response.
authors.affiliation: University of Groningen, Department of Chronobiology, Centre for Life Sciences, P.O. Box 11103, 9700CC Groningen, The Netherlands; University of Groningen, University Medical Center Groningen, Department of Psychiatry, University Medical Center Groningen, P.O. Box 30 001, 9700RB Groningen, The Netherlands. Electronic address: stefanknapen@gmail.com.
authors.forename: S E
authors.initials: SE
authors.lastname: Knapen
authors.affiliation: University of Groningen, Department of Chronobiology, Centre for Life Sciences, P.O. Box 11103, 9700CC Groningen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: van de Werken
authors.affiliation: University of Groningen, Department of Chronobiology, Centre for Life Sciences, P.O. Box 11103, 9700CC Groningen, The Netherlands; Chrono@Work B.V. Kadijk 1, 9747AT Groningen, The Netherlands.
authors.forename: M C M
authors.initials: MC
authors.lastname: Gordijn
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Psychiatry, University Medical Center Groningen, P.O. Box 30 001, 9700RB Groningen, The Netherlands.
authors.forename: Y
authors.initials: Y
authors.lastname: Meesters
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010789:Phototherapy; D012189:Retrospective Studies; D016574:Seasonal Affective Disorder / Q000628:therapy*
keywords: Depression; Expectations; Light therapy; Seasonal affective disorder