Evidence-based definitions of bipolar-I and bipolar-II disorders among 5,635 patients with major depressive episodes in the Bridge Study: validity and comorbidity

Abstract

The definitions of bipolar-I (BP-I) and bipolar-II (BP-II) disorders are currently under revision by the APA and by the WHO. We provide evidence of a revised set of criteria for bipolar disorders and major depressive disorder (MDD) which could serve to strengthen the construct and predictive validity of both disorders and enable more incisive studies of treatments and courses of both disorders. In the diagnostic Bridge Study of 5,635 patients with major depressive episodes from 18 countries (Europe, North Africa, Near East and Far East) leading psychiatrists in each country assessed a pre-specified group of symptoms, illness course, family history and duration of episodes; these data allowed tests of several definitions of bipolarity. The primary revised specifier diagnosis of BP-I disorder included manic episodes based on an additional category A criterion (increased activity/energy) and did not apply any exclusion criteria. The revised BP-II disorders included hypomanic episodes of 1-3 days. Family history and illness course validators (history of mania/hypomania among first degree relatives, 2 or more lifetime episodes and first symptoms having occurred before age 30) discriminated clearly between patients with bipolar-I or bipolar-II disorders meeting bipolarity specifier criteria and those with MDD. Specifier definitions provided better discrimination between MDD and the two bipolar subgroups. Patterns of concurrent comorbidities also differed significantly between patients meeting criteria for MDD compared with those meeting bipolar specifier criteria. Comorbidity patterns differed between bipolar-I and bipolar-II patients. This study provides evidence for the validity of modified (specifier) BP-I and BP-II definitions that incorporate illness course and family history which reduce ambiguities of major depressive episodes between bipolar-I and bipolar-II disorders and MDD.