Objective: Although cognitive impairment is an important clinical feature of bipolar disorder, it is unknown whether deficits are present at illness onset. The purpose of this study was to determine whether neuropsychological impairments are present in clinically stable patients with bipolar disorder shortly after resolution of their first manic episode.
Method: Within a large university medical center, 45 recently diagnosed (DSM-IV-TR) patients with bipolar disorder type I were evaluated after resolution of their first manic episode, along with 25 matched healthy comparison subjects. Participants were administered a neuropsychological battery evaluating 5 broad cognitive domains, including verbal/premorbid intellectual functioning, learning/memory, spatial/nonverbal reasoning, attention/processing speed, and executive function. Data were collected from July 2004 to August 2007.
Results: Relative to controls, patients showed broad impairments in learning/memory, spatial/nonverbal reasoning, executive function, and some aspects of attention (all P < .01). Specifically, deficits were evident on tests assessing sustained attention, attentional and mental set shifting, spatial working memory, nonverbal reasoning, and verbal learning and recall (all P < .01). Cognitive impairments in patients could not be fully attributed to substance abuse, medication status, or residual mood symptoms.
Conclusions: Results indicate that core neuropsychological deficits in sustained attention, learning and recall, spatial/nonverbal reasoning, and several aspects of executive function are present at illness onset. Cognitive deficits in bipolar disorder are, thus, most likely not exclusively attributable to progressive decline associated with increased illness burden, cumulative treatment effects, or chronicity of illness. These findings may provide etiologic clues into the illness and identify clinical targets for early treatment.
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