Differentiation of bipolar I and II disorders by examining for differences in severity of manic/hypomanic symptoms and the presence or absence of psychosis during that phase

BackgroundDSM-IV criteria for mania/hypomania overlap considerably. We sought to examine the utility of a model differentiating bipolar I and II disorders by weighting the presence or absence of psychosis during manic/hypomanic episodes as opposed to simply weighting symptom severity.MethodsA set of 632 patients with a so-assigned clinical bipolar I or II disorder diagnosis contributed to the principal analyses, and a subset of 210 was included in a comparative analyses of DSM-assigned diagnoses. We also examined the impact of duration of highs on symptom patterns and the extent to which depressive episodes were psychotic or non-psychotic melancholic in type.ResultsThere were no group differences for bipolar I and II patients (clinical or DSM groups) by age, gender, age of onset or age of formal bipolar diagnosis. Clinically assigned bipolar I patients returned higher severity scores than bipolar II patients on manic/hypomanic symptoms, but such differentiation was limited. Clinically-assigned bipolar I patients were more likely than bipolar II patients to be diagnosed with psychotic depression, and had lower rates of non-melancholic depression. Duration of highs had some impact on the phenomenology of highs, but not on the phenomenology of depression.LimitationsWe cannot establish the degree to which clinicians validly differentiated those with bipolar disorder, and accurately judged the lifetime presence of psychotic features and of depressive subtype differentiation.ConclusionsFindings support the utility of an alternative model to DSM-IV in weighting the respective presence or absence of psychotic symptoms during highs in differentiating bipolar I and II disorders.