The neurocognitive function of patients with major depression who fall into the “soft” bipolar spectrum resembles that of patients with bipolar II disorder rather than those with unipolar depression, say researchers.
These patients with major depression also had bipolar symptoms, but did not meet the threshold for a diagnosis of bipolar disorder.
“This finding reinforces the concern that individuals with [unipolar depression] who manifest bipolarity but do not meet the criteria for bipolar disorder by the DSM system per se may yet be ‘bipolar enough’ to be at risk of adverse reactions to antidepressant treatments”, say researchers Guiyun Xu (Guangzhou Psychiatric Hospital, China) and co-workers.
The patients were diagnosed according to the criteria in DSM-IV, but Xu et al note that the criteria for bipolarity are very similar in DSM-5, “which implies that a substantial proportion” of patients with soft bipolar spectrum disorders “may be still under the umbrella of” unipolar depression.
The team adds that “identifying these individuals is of scientific as well as clinical importance” because, among other things, they are at an increased risk of suicide.
Of the 300 patients with unipolar depression, 81 had evidence of bipolarity. These patients performed significantly better than those with “strict” unipolar depression in processing speed, visual-spatial memory and verbal working memory. And they performed better than 98 currently depressed patients with bipolar I disorder in set shifting and visual-spatial memory.
By contrast, patients in the soft bipolar spectrum did not significantly differ from 138 currently depressed patients with bipolar II disorder in any of the seven neurocognitive domains tested.
Soft bipolar spectrum patients also differed from those with unipolar depression on several clinical measures. They were younger at symptom onset (24.7 vs 31.1 years) and were more likely to have a family history of bipolar disorder (17.3 vs 8.6%) and at least three previous depressive episodes (28.4 vs 9%). They had more past hypomanic signs/symptoms than patients with unipolar depression, but fewer than those with bipolar I or II disorder.
“Our data provide evidence for the growing sense that a spectrum model of mood disorders more closely reflects the observed phenomena than a dichotomous model such as the DSM”, conclude the researchers in Bipolar Disorders.
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