Deficit form of bipolar disorder supported
MedWire News: Results from a Japanese study support the existence of a bipolar disorder subtype characterized by pervasive negative symptoms.
In a study of 494 outpatients evaluated at a psychiatric hospital in Tokyo in March 2007, the team found that seven patients (1.4%) fulfilled criteria for bipolar disorder with deficit syndrome (10.9% of 64 bipolar disorder patients).
"Although preliminary, the evidence on deficit status in patients with bipolar disorder that we found in this study appears more consistent with recent evidence and challenges the Kraepelinian dichotomy that reserves deficit status solely to schizophrenia patients," say Shintaro Nio (Keio University School of Medicine, Tokyo) and colleagues.
All of the patients were evaluated by an experienced psychiatrist, and the criteria for bipolar disorder with deficit syndrome were adopted from the original criteria for schizophrenia.
Specifically, deficit bipolar disorder was defined by the presence of at least two of the following six primary negative symptoms: restricted affect, diminished emotional range, poverty of speech, curbing of interests, diminished sense of purpose, and diminished social drive. These symptoms needed to have been present for at least the preceding 12 months, including during periods of clinical stability.
The researchers note that the seven patients meeting criteria for deficit bipolar disorder also had cognitive impairments of a similar severity to those usually observed in patients with schizophrenia.
Indeed, they had a mean total IQ score of 80.1 on the Wechsler Adult Intelligence Scale and a categories-achieved score of 0.4 on the Wisconsin Card Sorting Test.
"According to Kraepelin, schizophrenia is a disorder with an inevitably progressive course to dementia while bipolar disorder lacks such a deteriorating process," comment the researchers.
"The findings from our investigation, however, indicate that a deficit form of bipolar disorder may exist," they add. "In other words, it may be possible that some patients with bipolar disorder develop a deficit form that is akin to schizophrenia."
Nio and team conclude in the Journal of Affective Disorders: "In light of the paucity of data on 'deficit' bipolar disorder, further investigations are apparently needed to shed more light on this clinically relevant issue."
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By Mark Cowen