Can chronotype function as predictor of a persistent course of depressive and anxiety disorder?

BACKGROUND: The role of chronotype, the individual timing of sleep/activity, has been studied in relation to depressive and anxiety disorders. A cross-sectional association between a depressive episode and evening-type has been identified. However, until now the predicting capacity of chronotype concerning persistence of psychiatric disorders remains unclear. Our aim is to examine whether a later chronotype in patients with a depressive and/or anxiety disorder can serve as a predictor of a persistent course. METHODS: A subsample of patients with a depressive and/or anxiety disorder diagnosis and chronotype data of the longitudinal Netherlands Study of Depression and Anxiety (NESDA) was used. Diagnosis of depressive and anxiety disorders (1-month DSM-IV based diagnosis) were determined at baseline (n = 505). From this group persistence was determined at 2-year (FU2) (persistent course: n = 248, non-persistent course: n = 208) and 4-year follow-up (FU4) (persistent course: n = 151, non-persistent course: n = 264). Chronotype was assessed at baseline with the Munich Chronotype Questionnaire. RESULTS: A later chronotype did not predict a persistent course of depressive and/or anxiety disorder at FU2 (OR (95% CI) = 0.99 (0.83-1.19), P = 0.92) or at FU4 (OR (95% CI) = 0.94 (0.77-1.15), P = 0.57). LIMITATIONS: Persistence was defined as having a diagnosis of depressive and/or anxiety disorder at the two-year and four-year follow-up, patients may have remitted and relapsed between assessments. CONCLUSION: Chronotype, measured as actual sleep timing, of patients with a depressive or anxiety disorder did not predict a persistent course which suggests it might be unsuitable as predictive tool in clinical settings.

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

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.