Social rhythms and vulnerability to bipolar disorder

Background: Reduced social rhythmicity is a commonly reported feature of bipolar disorder which may extend to non-clinical populations at risk of bipolar disorder. The aim of the current study was to investigate social rhythms across three groups of participants; a clinical group of bipolar disorder outpatients, and two non-clinical groups with high- and low-vulnerability to bipolar disorder, respectively. It was expected that reduced social rhythmicity would differentiate the clinical group from the low-vulnerability group, but not the high vulnerability group. Methods: Non-clinical participants were selected on the basis of scores derived from the General Behaviour Inventory and allocated to groups of high (n = 36) and low (n = 36) trait vulnerability to bipolar disorder. The clinical group (n = 15) were volunteers recruited from an outpatient clinic. Participants completed a self-report social rhythmicity measure daily for seven consecutive days. Results: One-way analysis of covariance (age) showed a significant overall effect for group, F (2,83) = 4.67, p < .05. Post hoc comparisons revealed significant differences in social rhythms between the two nonclinical groups only. Limitations: The cross-sectional design of the study limits the strength of conclusions that can be drawn. Conclusions: The hypothesis was only partially supported. Consistent with expectations, the non-clinical group with higher vulnerability to bipolar disorder recorded lower social rhythmicity than the non-clinical group with lower vulnerability to bipolar disorder. The clinical group however, did not differ in social rhythmicity from the lower vulnerability group. The findings may have consequences for the way in which vulnerability to bipolar disorder is managed. (C) 2011 Elsevier B.V. All rights reserved.