Validating the soft bipolar spectrum in the French National EPIDEP Study: The prominence of BP-II 1/2

Abstract

Background Much of the current literature on bipolar disorder is focused on bipolar I (BP-I), and to a much lesser extent on bipolar II (BP-II). The French multi-center national EPIDEP study has, among its objectives, the feasibility of validating a broader spectrum of bipolarity (the so-called “soft spectrum”) by practicing clinicians. In this report we test aspects of a bipolar schema proposed earlier by Akiskal and Pinto [Akiskal, H.S., Pinto, O., 1999. The evolving bipolar spectrum: Prototypes I, II, III, IV. Psychiatr. Clin. North Am. 22: 517–534.]. Methods EPIDEP was scheduled in three phases: Phase 1 to recruit DSM-IV major depressives; Phase 2 to assess hypomania and affective temperaments; and Phase 3 to obtain history on course of illness, family history, and comorbidity. Comparative analyses are presented between affective subgroups constructed on a hierarchical basis: spontaneous hypomania (BP-II), cyclothymic temperament (BP-II 1/2), antidepressant-associated hypomania (BP-III), hyperthymic temperament (BP-IV), versus “strict unipolar” (UP). Results We present data on 490 patients for whom we obtained full assessment during all three phases of the study, classified as BP-II 1/2 ( N = 164), II ( N = 61), III ( N = 28), IV ( N = 22), as well as UP ( N = 174) as the reference nonbipolar group. Systematic inter-group comparison among the soft spectrum showed significant differences along clinical, descriptive, course, pharmacologic response and familial affective disorder patterns, which confirm the heterogeneity of the soft bipolar spectrum, with special characteristics for each of the subgroups. In terms of external validation, familial bipolar loading characterized all soft bipolar subgroups except type IV. Limitation Data collection conducted in a practice setting, clinicians cannot be entirely held “blind” to all measures. This is an exploratory attempt, with many variables examined, to help characterize the clinical terrain of soft bipolarity. Conclusion This is nonetheless the first systematic clinical attempt to validate the bipolar spectrum beyond mania (BP-I). BP-II 1/2, BP-III and BP-IV appeared distinct from BP-II and strict UP — along most of the variables examined. BP-II 1/2 – with early onset complex temperament structure, and high mood instability, rapid switching, irritable (“dark”) hypomania and suicidality – emerged as the most prevalent and severe expression of the bipolar spectrum, and accounting for 33% of all MDE. These results, which are of great public health relevance, testify to the cyclic nature of bipolarity in its softest expressions. The soft phenotypes are also of interest for genetic investigations of bipolar disorder.