A study designed to determine differential characteristics between bipolar disorder (BD)-I and BD-II and published in Psychiatry Research found that being female, having a family history of psychiatric conditions, and having higher illness severity were associated with a diagnosis of BD-II.

Gianluca Serafini, MD, PhD, of the Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, Section of Psychiatry, University of Genoa, Italy, and colleagues conducted a study of bipolar subtype characteristics among patients with currently euthymic bipolar disorder. Patients were receiving only maintenance treatment.

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The investigators found that those with BD-II were more likely to be female (odds ratio [OR], 0.289), to have other family members with psychiatric conditions (OR, 0.273), and to experience a higher severity of illness (OR, 0.604). In addition, patients with BD-II were more likely to have psychotic symptoms at first episode and to have substance abuse/dependence issues. Those with BD-I were more likely to have higher depressive, manic, anxiety, and symptoms severity and to have been younger at illness onset. 

Limitations of the study include the use of a single psychiatric sample population and the relatively small sample size, making it difficult to generalize these findings to other existing patient populations. In addition, the subgroups compared included both outpatients and inpatients, possibly biasing the results.

The investigators concluded that BD is a heterogeneous condition and there is a need to identify valid and reliable BD subtypes according to phenotypic BD characteristics. These findings also challenge the assumption that BD-II is a less severe and disabling BD subtype.  

Reference

Serafini G, Gonda X, Aguglia A, et al. Bipolar subtypes and their clinical correlates in a sample of 391 bipolar individuals. Psychiatry Res. 2019;281:112528.