Background The purpose of this study is to determine clinical characteristics of patients who are diagnosed “Bipolar Not Otherwise Specified” (BP NOS) and are considered part of the bipolar spectrum. The lifetime prevalence of bipolar disorder in the general population may be as high as 6% when the full spectrum of bipolar disorders is accounted for. Our hypothesis was that patients with BP NOS would be more similar to other bipolar patients than Major Depressive Disorder (MDD) patients regarding age of onset, history of suicidal behavior and family history of bipolar disorder.
Study Design and Methods We conducted a retrospective chart review to extract and analyze data on family history, course and clinical characteristics of 340 Bipolar I (BP I), Bipolar II (BP II), Bipolar Not Otherwise Specified (BP NOS) or Major Depressive Disorder (MDD) patients who were then grouped by diagnosis for analysis. Nominal variables were compared between groups using chi-squared tests and ANOVA was used to compare means between groups for continuous variables. Significant F values were followed by independent-samples t-tests.
Results Patients with BP I, BP II and BP NOS were all found to have a significantly earlier mean age onset of depression than MDD Single, MDD Recurrent and MDD with treatment induced hypomania patients. A significantly higher incidence of bipolar illness in a first degree relative was found for all of the BP groups (27-32%) when compared to MDD Single (11%) and MDD Recurrent (11%) groups. Only BP I had a significantly higher rate of suicide attempts (42%) compared to BP NOS (17%) and MDD Recurrent (16%).
Conclusions Our data supports the assertions of others that early age of onset and positive family history of bipolar illness are associated not only with Bipolar I and II but ‘softer' forms of bipolar illness which the Diagnostic and Statistical Manual of Mental Disorders IV classifies as BP NOS and current literature refers to as a category of ‘bipolar spectrum disorder' albeit with varying proposed definitions and diagnostic criteria. Suicide attempt history may be more useful in identifying severity of illness than distinguishing the bipolar spectrum from depressive disorders. Further research is needed to clearly define the boundaries of the bipolar spectrum and whether or not depressed patients with treatment induced hypomania belong in the bipolar spectrum category.
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