title: Does age at onset support a dimensional relationship between Bipolar II disorder and major depressive disorder?
abstract: The current categorical splitting of bipolar and depressive disorders has been questioned. Age at onset is an important variable used to support such a division. Study aim was to assess the distribution of age at onset between bipolar II disorder (BP-II) and major depressive disorder (MDD), and onset age-bipolar family history, onset age-BP-II diagnosis dose-response relationships. No bi-modal distribution and no presence of dose-response relationships would not support a categorical distinction between BP-II and MDD. Consecutive 389 BP-II and 261 MDD major depressive episode (MDE) outpatients were interviewed with the DSM-IV Structured Clinical Interview and the Family History Screen, by a mood specialist psychiatrist in a private practice. Age at onset was defined as age at onset of the first MDE. Distribution of age at onset between BP-II and MDD was studied by Kernel density estimate and histogram methods, dose-response relationships by ROC analysis. BP-II, versus MDD, had significantly lower age at onset, more recurrences, and more bipolar family history. Kernel density estimate and histogram distributions of age at onset showed no bi-modality. Likelihood ratios between age at onset and bipolar family history loading, and between age at onset and BP-II diagnosis, showed dose-response relationships. The bi-modality and dose-response approaches, versus classic diagnostic validators, seem to support a dimensional relationship between BP-II and MDD.
authors: Hecker Psychiatry Research Center, Forli, Italy. francobenazzi@fbenazzi.it
authors: Franco
authors: F
authors: Benazzi
mesh_terms: D000367:Age Factors; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics; D040741:Genetic Load; D006801:Humans; D016015:Logistic Models; D011379:Prognosis; D012372:ROC Curve; D012307:Risk Factors; D013223:Statistics as Topic