Affective temperament, impulsivity and biological rhythms in bipolar disorder: A case-sibling-control study

This study examined the relationships between affective temperaments, impulsivity, and sleep-related biological rhythm disturbances in euthymic patients with bipolar disorder (BD), their unaffected siblings, and healthy controls. The sample included 82 patients with BD type I, 57 siblings, and 70 healthy controls. Participants completed the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego Autoquestionnaire (TEMPS-A), the Barratt Impulsiveness Scale (BIS-11), and the Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN). Group comparisons, correlation analyses, hierarchical regression, and mediation analyses were performed. Patients with BD showed higher depressive, cyclothymic, irritable, and anxious temperament scores than siblings and controls, while hyperthymic temperament did not differ between groups. Siblings displayed intermediate temperament and impulsivity profiles without significant sleep-related rhythm disturbance. Patients also exhibited higher total and attentional impulsivity scores and greater sleep-related rhythm disturbance than healthy controls. Regression analyses indicated that anxious temperament and impulsivity were positively associated with sleep-related rhythm disturbance. Mediation analyses revealed that impulsivity fully mediated the relationship between irritable temperament and sleep-related rhythm disturbance and partially mediated the effect of anxious temperament. Hyperthymic temperament was associated with lower impulsivity and rhythm disturbance measures. These findings suggest that anxious and irritable temperaments are linked to sleep-related rhythm disturbances in BD partly through increased impulsivity, highlighting impulsivity as a potential target for rhythm-focused interventions..