Chronotype is associated with affective temperaments, clinical severity and worse treatment outcomes in bipolar disorders: results from a two-center, cross-sectional study.

Objective: The present study was aimed at investigating the clinical correlates of evening chronotype in a population of subjects suffering from bipolar disorders (BD).

Methods: We assessed chronotype using the Morningness-Eveningness Questionnaire. We administered the brief Temperament Evaluation of Memphis, Pisa, and San Diego, the Barratt Impulsiveness Scale, and the Alda Scale to evaluate affective temperaments, impulsiveness, and response to mood stabilisers. We performed bivariate analyses and ran a logistic regression model to analyse clinical variables associated with evening chronotype.

Results: In our sample (n = 178), subjects with an evening chronotype (n = 56, 31.5%) more often suffered from BD type I and reported higher prevalence of seasonality, antidepressant-induced mood switches, psychotic, aggressive, mixed, and anxiety features, and substance use disorders. The number of lifetime suicide attempts and mood episodes was higher in this subgroup. Depressive, cyclothymic, irritable, and anxious temperament scores were higher among evening-chronotype subjects, who also displayed greater levels of impulsiveness and worse treatment response. At the logistic regression, evening chronotype was associated with depressive and irritable temperaments.

Conclusions: Subjects with evening chronotype display higher clinical severity and worse BD course. Clinicians should evaluate the presence of evening chronotype in BD subjects, especially in those with irritable or depressive temperament.Key pointsEvening chronotype is a frequent clinical feature in subjects suffering from bipolar disorders (BD);Affective temperaments, particularly depressive and irritable, are associated with evening chronotype in BD;Evening chronotype underpins higher severity of the clinical picture in BD, as well as a worse response to mood stabiliser treatment;Circadian preferences should be systematically assessed in subjects suffering from BD, with particular attention to evening preference.