By Lucy Piper, Senior medwireNews Reporter
Researchers believe that the DSM 4-day duration criterion for diagnosing bipolar II disorder is no longer valid and its continued use could exclude a large number of patients with true bipolar II disorder.
They found that 186 bipolar II disorder patients who met the 4-day criteria did not differ significantly from 315 patients whose manic episode lasted less than 4 days on a number of illness correlates on the Mood Swings Questionnaire (MSQ).
These included age of onset of depression and manic episodes, age when formally diagnosed with bipolar disorder, rates of hospitalization for depressive episodes, and rates of depression and bipolar disorder in first-degree relatives.
“Our study findings are strongly consistent with previous studies arguing that the clinical phenotype of [bipolar] II disorder (and its existence) is not dependent on a minimum duration of four 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,” the researchers Gordon Parker (Prince of Wales Hospital, Sydney, Australia) and colleagues comment.
The only difference was that patients with brief manic episodes were more likely to rate manic symptoms as being less severe than those whose episodes lasted for 4 days. The average total MSQ scores were 49.6 and 57.0, respectively.
Significant differences were seen for most of the MSQ subscales, including: mood elevation (13.6 vs 15.9 for the brief and 4-day groups, respectively); mysticism (3.5 vs 4.4, respectively); irritability (5.7 vs 5.5, respectively); and disinhibition (6.1 vs 6.8).
Similar findings were also seen on the Mood Disorders Questionnaire (MDQ). However, the researchers note that while the differences in MSQ and MDQ are formally significant, they are relatively slight.
The findings suggest that rather than the two groups differing in terms of experiencing hypomanic symptoms, the difference is in the intensity of the episodes.
“A plausible explanation is that those with a [bipolar] II disorder experiencing longer episodes tend to also have somewhat more severe hypomanic episodes,” the researchers write in the Journal of Affective Disorders.
They are concerned that if the current DSM-5 duration criterion continues to be used, then some patients with bipolar II disorder will go undiagnosed.
“If our sample is indicative, the duration criterion may exclude the majority – in that 63% of our sample comprised the ‘brief’ group,” the team points out.
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