Evening Chronotype is Associated with Impulsivity and Diminished Resilience in Bipolar Disorder: Potential Link with Early Life Stressors May Affect Mood Features and Suicidal Risk

The study aimed at investigating the possible effects of early stressful experiences on chronotype and the clinical features associated with bipolar disorder (BD). A sample of 203 adults with BD depressive episode (mean age 46.7 + 13.5, females 57.1 %) was assessed by the Beck Depression Inventory-II (BDI-II), the Early Trauma Inventory Self Report-Short Form (ETISR-SF), the Difficulties in Emotion Regulation Scale (DERS), the Morningness-Eveningness Questionnaire (MEQ), the Resilience Scale for Adults (RSA), the Scale for Suicide Ideation (SSI) and the Young Mania Rating Scale (YMRS). Patients with evening chronotype showed greater early life stressors and greater severity of depressive symptoms, anxiety comorbidity, higher suicidal risk, emotional impulsivity and low resilience. In logistic regression models, evening chronotype (MEQ) was a significant predictor of depressive symptoms (BDI-II > 13; odds ratio [OR] = 4.41; 95 % CI 1.89-9.01; p < 0.001), mixed features (YMRS>5; OR = 2.60; 95 % CI 1.36-4.97; p = 0.004), a higher risk of suicidality (SSI > 6; OR = 2.27; p = 0.020), emotional dysregulation (DERS; OR = 2.01; 95 % CI 1.09-3.74; p = 0.027), and low resilience (RSA < 89; OR = 1.99; 95 % CI 1.12 = 3.93, p = 0.046). Mediation analyses revealed that an evening chronotype might play a mediating role in the relationship between early life stressors and high suicidal risk (Z = 2.0, SE = 0.62, p = 0.044), emotional impulsivity (Z = 2.07, SE = 0.33, p = 0.038), and low resilience in social competence (Z = 2.08, SE = 0.02, p = 0.037). Addressing circadian rhythm alterations in subjects exposed to early stressors may help preventing consequences of those stressors on BD.