Seasonal pattern and bipolar disorder

A novel positive association of seasonal pattern with undetermined predominant polarity and aggressive behaviour has been outlined. Moreover, a positive association with bipolar disorder subtype II was confirmed. If factors related to the seasonal pattern are better understood, a subgroup of bipolar disorder patients with a more homogeneous disease course may be identified, aiding insights into pathways and subsequently development of new therapies [1].

A seasonal pattern is a bipolar disorder specifier to indicate a clinical course characterised by a tendency towards relapses during specific moments of the year [2]. Manic episodes peak during spring/summer and to a lesser extent in autumn. Depressive episodes peak in early winter and to a lesser extent in summer. A seasonal pattern is predominantly seen in countries in the northern or southern hemisphere, but hardly in equatorial regions. There may be several different factors that influence the occurrence of seasonal pattern, for example, sleep deprivation, circadian gene variations, and climatic factors. Until now, seasonal pattern was only investigated for depressive episodes. In the DSM-5, seasonal pattern may be applied to both depressive and manic episodes. The current study investigated the association between seasonal pattern and bipolar disorder according to this new DSM-5 definition [1].

Enrolled were 708 patients with bipolar disorder subtype I or II. Data for seasonal pattern was obtained from electronic clinical records containing season of relapse and type of episode per season. Both groups were matched for socio-demographic and clinical correlates.

A seasonal pattern was seen in 16.5% of patients. There was a positive association of seasonal pattern with a diagnosis of bipolar disorder subtype II (P<0.001) and bipolar disorder with undetermined predominant polarity (P=0.001). Seasonal patterns were negatively associated with a predominantly manic polarity (P=0.004), presence of psychotic symptoms during mood episodes (P<0.001), aggressive behaviour (P=0.001), and lifetime number of hospitalisations (P<0.001). The total variance explained by the model was statistically significant (P=0.003) and included a significant contribution of bipolar disorder subtype II, undetermined predominant polarity, and aggressive behaviour.

 

1. Fico G, et al. Bloomed again: seasonality and clinical correlates in bipolar disorder. P.354. ECNP Congress 2020.
2. Geoffrey PA, et al. J. Affect. Dis. 2014;168:210-223.

Posted on 2 November, 20205 August, 2021