Daytime napping and depressive symptoms in bipolar disorder: A cross-sectional analysis of the APPLE cohort

Background

The relationship between daytime napping and depression remains debatable. Thus, we investigated whether daytime napping is associated with depressive symptoms in patients with bipolar disorder.

Methods

In a cross-sectional study, we enrolled 204 outpatients with bipolar disorder who were participants in the Association between Pathology of Bipolar Disorder and Light Exposure in Daily Life (APPLE) cohort study. Each participant's daytime napping was measured using an actigraph over 7 consecutive days. Depressive symptoms were evaluated using the Montgomery–Åsberg Depression Rating Scale, and scores of ≥8 points were considered indicative of a depressed state.

Results

One-hundred and ten (53.9 %) participants were depressed. In multivariable logistic regression analysis, as the number of nap days, number of naps per day, and nap duration increased, the odds ratio (OR) for depressed state significantly increased. Additionally, compared to the participants who did not nap, the participants who napped on five or more days a week or who had an average nap duration over 60 min had more than three times higher ORs in the depressed state (number of nap days: OR, 3.66; 95 % confidence interval [CI], 1.32–10.17; nap duration: OR, 3.14; 95 % CI, 1.12–8.81).

Conclusions

We found a significant and independent association between daytime napping and depressive symptoms in patients with bipolar disorder. Further studies are warranted to identify the effect of short napping on depressive symptoms in patients with bipolar disorder.