High Prevalence of Bipolar Spectrum Disorders

Letter to the Editor

Sir: I read with interest the Journal article by Ghaemi et al. (October 2000) reporting that bipolar spectrum disorders were very common (found in 60% of their sample) and that many subjects diagnosed with "unipolar" depression (56%) were found to have bipolar disorder in a primary care psychiatric setting when patient assessment was made by trained clinicians who systematically and carefully interviewed about past hypomania. These findings support recent studies showing that, in samples of depressed outpatients, the prevalence of bipolar II disorder was 30% to 50%. A community prevalence of bipolar spectrum disorders of 3% to 8.3% has been reported, whereas a 0.5% community prevalence was reported in DSM-IV. The apparent increased prevalence of bipolar II disorder in these recent studies may be related to systematic questioning about past hypomania of depressed patients and the use of a criterion of a minimum duration of hypomania shorter than the 4 days specified by DSM-IV (a cutoff not based on data).