Seasonal pattern of manic episode admissions among bipolar I disorder patients is associated with male gender and presence of psychotic features.

Background: Bipolar I disorder (BD-I) patients demonstrate disrupted chronobiology expressed as seasonal variation in mood symptoms. The seasonal pattern (SP) specifier of mood disorders was recently extended by the DSM-5, to be applied to manic episodes. However, the significance of seasonality of manic episodes for the course of BD-I is unknown. In the present study we sought to identify clinical and demographic features that discriminate between BD-I patients with and without SP of manic admissions.

Methods: BD-I patients (n=148) admitted at least twice with the same mood exacerbation type, were retrospectively followed between 2005 and 2013. Demographic and clinical characteristics were compared between BD-I patients with or without SP of manic admissions.

Results: SP of manic episode admissions, found in 31 (26%) of 117 BD-I patients with repeated manic episode admissions, was associated with higher rates of male gender (p=0.01), presence of psychotic features (p=0.01) and comorbid substance use disorder (p<0.05) compared to patients without SP. In a multivariate analysis, SP of manic episode admissions was associated with the presence of psychotic features (OR 8.42, 95% CI: 1.05-67.65, p<0.05) and male gender (OR 3.23, 95% CI: 1.08-9.65, p<0.05), but not with comorbidity of substance use disorder (OR 1.79, 95% CI: 0.71-4.50, p=0.24).

Limitations: Seasonal psychological/environmental factors contributing to the emergent of mood episodes could not be ruled out.

Conclusions: Our results suggest that SP of manic admissions is associated with male gender and the presence of psychotic features, thus might be associated with more severe form of the disorder.