Biological rhythm impairment in bipolar disorder: A state or trait marker?

CONTEXT: There is limited research on biological rhythms in bipolar disorder (BD) from the Indian setting despite its intricate relationship with metabolic syndrome (MS) and functioning. AIMS: The study aimed to assess “trait marker” status of biological rhythms as well as correlates of biological rhythm impairment in euthymic BD. SETTING AND DESIGN: Cross-sectional observational study over 6 months was carried out in hospital setting. MATERIALS AND METHODS: Biological Rhythms Interview of Assessment in Neuropsychiatry Questionnaire (BRIAN) and Functioning Assessment Short Test (FAST) were used to assess biological rhythms and functioning, respectively. MS was diagnosed as per modified National Cholesterol Education Program– Adult Treatment Panel III. Depressive symptoms were assessed by the Hamilton Depression Rating Scale (HDRS). Euthymia was defined as symptomatic remission for at least 8 weeks. Ethical approval was taken. RESULTS: Fifty cases of euthymic BD and fifty apparently healthy controls were recruited. Total as well as certain domain-specific BRIAN and FAST scores were significantly higher in cases compared to controls. A significant positive correlation was found between the total BRIAN score with HDRS as well as FAST score. No correlation was obtained between biological rhythms and metabolic parameters. CONCLUSIONS: Our results support the hypothesis that biological rhythm impairment is a trait marker in patients with BD. The study supports the need for management of subsyndromal depressive symptoms even in inter-episodic period.