The DSM criteria requiring a duration of 4 or more days for the diagnosis of a hypomanic episode are unnecessary for the clinical definition of bipolar II disorder. These criteria probably also exclude patients who truly have the condition, according to an Australian study published in the Journal of Affective Disorders.
The investigators compared responses on the Mood Swings Questionnaire (MSQ) and the Mood Disorders Questionnaire (MDQ) from 315 adult patients diagnosed with bipolar II (BP II) disorder whose hypomanic episodes lasted less than 4 days, and 186 whose episodes met the DSM criteria of lasting 4 or more days. The mean age of both groups was about 35 years, and about 60% of each were women (J. Affect. Disord. 2014;156:87-91).
The mean total MSQ score was 49.6 in the brief-episode group and 57.0 in the standard-duration group, with the brief group also reporting slightly lower scores on most MSQ subscales. Results were similar on the MDQ among those who completed it, with the brief-duration group returning significantly lower scores on 6 of the 13 items, and a somewhat lower total score (9.5 vs. 10.3; P less than .05).
Overall, patients whose hypomania lasts less than 4 days scored 14% lower on the MSQ and 8% lower on the MDQ, "which, while formally significant, are relatively slight differences ... . A plausible explanation is that those with BP II disorder experiencing longer episodes tend to also have somewhat more severe hypomanic episodes," said Dr. Gordon Parker, of the University of New South Wales in Sydney, Australia, and his associates.
Dr. Gordon Parker
"Our study findings are strongly consistent with previous studies arguing that the clinical phenotype of BP II disorder ... is not dependent on a minimum duration of 4 days as imposed by DSM-IV and DSM-5, but further advanced by validation against a number of clinical correlates and not simply by examining phenomenological expression," Dr. Parker and his associates wrote.
"The current DSM-5 imposition therefore continues to risk those with a true bipolar disorder being excluded from receiving such a diagnosis. If our sample is indicative, the duration criterion may exclude the majority – in that 63% of our sample comprised the ‘brief’ group."
The two groups did not differ significantly in age of onset of depression and hypomania, age at formal diagnosis, and other key variables. Rates of bipolar disorder in first-degree relatives were comparable across the two groups, at a bit under 40% in each. "We interpret [that] finding ... as being a distinctive one, and supporting the validity of brief BP II states," the investigators said.
However, "the possibility of false positive BP II diagnoses, especially with brief hypomanic episodes, must be conceded while our examination of clinical symptoms was limited to two measures," they wrote, citing one of several limitations.
The authors said they had no relevant financial disclosures. The study was funded by the National Health and Medical Research Council of Australia and the New South Wales Department of Health.