Association between affective temperaments and mood features in bipolar disorder II: The role of insomnia and chronobiological rhythms desynchronization.

Background: Bipolar disorders are complex disorders involving the interaction of multiple factors. Affective temperaments, insomnia, and chronobiological rhythms desynchronization may all contribute to bipolar disorder. Since there is a paucity of research examining this topic we aimed to study how they are interrelated and collectively associated with clinical features of bipolar disorder.

Method: One-hundred patients with Bipolar Disorder type II depressive episode with and without mixed features were recruited and compared. Subjects were evaluated with SCID -5, the Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN), the Insomnia Severity Index (ISI), and the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego Auto-questionnaire (TEMPS-A) while evaluating depressive (Beck Depression Inventory-BDI-II) and manic (Young Mania Rating Scale-YMRS) symptoms. Logistic regression and mediation analyses were conducted.

Results: Subjects with mixed features showed a higher scores in both insomnia and chronobiological rhythms scores. When considering affective temperaments not only depressive, cyclothymic and irritable temperaments predicted mood symptoms but also insomnia (depressive symptoms O.R. 4.17, p = 0.043) and chronobiological sleep de-synchronization (manic symptoms O.R. 8.69, p = 0.001). Insomnia symptoms and chronobiological alterations mediated the association between affective temperaments and mood symptoms.

Limitations: the cross-sectional design limited any causal interpretation.

Conclusion: Subjects with mixed features showed a greater severity of insomnia and chronobiological rhythm de-synchronization compared to subjects without. Insomnia and chronobiological alterations may contribute to mood disorders together with affective temperaments in a complex interplay also mediating their effect on mood. Preventive strategies for bipolars should also act on the dysregulation of sleep and circadian rhythms.