Unipolar mania confirmed as distinct subtype of bipolar disorder
medwireNews: Unipolar mania (UM) is a distinct subtype of bipolar I disorder which, when accompanied by generalised anxiety disorder (GAD) and attention deficit hyperactivity disorder (ADHD), can predict transition to classic bipolar disorder, say US researchers.
“Comorbid anxiety disorder is closely connected to a poor clinical course of bipolar disorder”, remark Andrew Nierenberg from Harvard Medical School in Boston, Massachusetts, and colleagues in Depression and Anxiety.
Among the 1411 patients from the National Epidemiological Survey on Alcohol and Related Conditions (NESARC) whose data were included in the current study, 34% experienced a manic episode during the 3-year follow-up. However, the prevalence of UM was low according to each of the three UM definitions used, at 7.2% for group 1 (at least three manic episodes and no depression in more than 5 years' illness), 6.9% for group 2 (at least four manic episodes and no depression in 4 or more years' illness) and 5.0% for group 3 (at least three major affective episodes in 10 years' illness).
Regardless of definition used, UM patients were significantly more likely to be non-White and male, and had lower rates of panic disorder, agoraphobia without panic disorder, social phobia and GAD, compared with their classic bipolar disorder counterparts, observes the research team.
In a subset of 1172 of the study participants re-interviewed 3 years after initial study entry, those with UM were significantly less likely to have developed major depressive episodes than their counterparts with classic bipolar disorder, with odds ratios (OR) ranging from 0.30 to 0.47 depending on the definition. Notably, the UM group had similar odds of experiencing such episodes as individuals with neither classic bipolar disorder nor UM.
The risk of having transitioned to classic bipolar disorder between the initial study period and re-interview 3 years later was significantly associated with presence of comorbid GAD and ADHD, with these increasing the risk about twofold, report Nierenberg and co-workers.
They suggest therefore that comorbid GAD and ADHD could be related to more severe psychopathology of bipolar disorder, including major depressive episodes.
“Further studies are warranted in order to confirm the definition of UM and explore the underlying biological differences”, they conclude.
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By Sarah Pritchard, medwireNews Reporter