Circadian rhythm sleep-wake disorders as predictors for bipolar disorder in patients with remitted mood disorders

Background: Circadian rhythm dysfunction is thought to play a key role in the pathogenesis of bipolar disorder (BD). We focused on circadian rhythm sleep-wake disorders (CRSWD) as possible predictors for bipolar disorder in patients with remitted mood disorders. Method: One hundred four BD (41 type I and 63 type II) outpatients and 73 age-and sex-matched major depressive disorder (MDD) outpatients participated in this study. The subjects were asked to answer questionnaires including demographic variables, clinical course of the disorder, and family history of psychiatric disorders. Severity of mood status was evaluated by the Montgomery-Asberg Depression Rating Scale and Young Mania Rating Scale. CRSWD was diagnosed by clinical interview and sleep logs based on the International Classification of Sleep Disorders, third edition. Results: The rate of CRSWD in BD subjects was significantly higher than that in MDD subjects (33.7% vs 9.6%; P < 0.001). A multiple logistic regression analysis revealed that comorbid CRSWD (OR = 3.35, 95% CI = 1.24-9.07; P = 0.018), two or more previous mood episodes within the past year (OR = 3.57, 95% CI = 1.10-11.63; P = 0.035), and antidepressant-related switch to mania/hypomania (OR = 10.01, 95% CI = 1.20 - 83.52; P = 0.033) were significantly associated with BD in patients with remitted mood disorders. Conclusion: CRSWD, as well as other factors, could be diagnostic predictors for BD in patients with remitted mood disorders. Combinations of these factors might be useful for predicting a BD diagnosis among the mood disorders in a clinical setting.