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J Affect Disord. 2014 Sep;166:343-6. doi: 10.1016/j.jad.2014.05.034. Epub 2014 Jun 2.

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

Author information

1
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.
2
University of Groningen, Department of Chronobiology, Centre for Life Sciences, P.O. Box 11103, 9700CC Groningen, The Netherlands.
3
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.
4
University of Groningen, University Medical Center Groningen, Department of Psychiatry, University Medical Center Groningen, P.O. Box 30 001, 9700RB Groningen, The Netherlands.

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).

LIMITATIONS:

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.

KEYWORDS:

Depression; Expectations; Light therapy; Seasonal affective disorder

PMID:
25012451
DOI:
10.1016/j.jad.2014.05.034
[Indexed for MEDLINE]
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