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Factor structure of hypomania: interrelationships with cyclothymia and the soft bipolar spectrum
Elie G Hantouche1, Jules Angst, Hagop S Akiskal
1Psychiatry Department, Mood Center, Pitié-Salpetriere Hospital, Paris, France.
Background:
No systematic data exists on the phenomenology and psychometric aspects of hypomania. In this report we focus on the factor structure of hypomania and its relationships with cyclothymic temperament in unipolar (UP) and bipolar II (BP-II) spectrum (soft bipolar) patients.
Method:
The combined sample of UP and BP-II spectrum patients (n=427) derives from the French National multi-center study (EPIDEP). The study involved training 48 psychiatrists at 15 sites in France in a protocol based on DSM-IV phenomenological criteria for major depressive disorder, hypomania, and BP-II, as well as a broadened definition of soft bipolarity. Psychometric measures included Angst's Hypomania Checklist (HCA) and Akiskal's Cyclothymic Temperament (CT) Questionnaires.
Results:
In the combined sample of the UP and BP-II spectrum, the factor pattern based on the HCA was characterized by the presence of one hypomanic component. In the soft bipolar group (n=191), two components were identified before and after varimax rotation. The first factor (F-1) identified hypomania with positive (driven-euphoric) features, and the second factor (F-2) hypomania with greater irritability and risk-taking. In exploratory analyses, both factors of hypomania tentatively distinguished most soft BP subtypes from UP. However, F-1 was generic across the soft spectrum, whereas F-2 was rather specific for II-1/2 (i.e., BP-II arising from CT). CT, which was found to conform to a single factor among the soft bipolar patients, was significantly correlated only with irritable risk-taking hypomania (F-2).
Limitation:
In a study conducted in a clinical setting, psychiatrists cannot be kept blind of the data revealed in the various clinical evaluations and instruments. However, the systematic collection of all data tended to minimize biases.
Conclusion:
EPIDEP data revealed a dual structure of hypomania with 'classic' driven-euphoric contrasted with irritable risk-taking expressions distributed differentially across the soft bipolar spectrum. Only the latter correlated significantly with cyclothymic temperament, suggesting the hypothesis that repeated brief swings into hypomania tend to destabilize soft bipolar conditions.