Predominant polarity, polarity index, and treatment selection in bipolar disorder

Bipolar disorder (BD) is a chronic and disabling illness, with lifetime prevalence of 2.4% worldwide. Predominant polarity (PP), ie, depressive versus manic, may influence illness characteristics, treatment selection, and outcomes in BD. PP has been proposed as a course specifier for BD, although not included in the Diagnostic and Statistical Manual of Mental Disorders (5th edn) (DSM-5). The polarity index (PI), a metric algorithm that reflects antimanic versus antidepressant maintenance efficacy of available treatments for BD, is calculated as the ratio of number needed to treat (NNT) for prevention of depression and NNT for prevention of mania. Evidence indicates that the net PI of ongoing maintenance-treatment regimens for BD is related to the patient’s PP. Additionatlly, PP and PI may aid in treatment selection and outcome prediction in BD. Therefore, this chapter provides an overview of putative roles of PP and PI in the course and treatment selection for BD.