Cognitive deficits present at bipolar disorder onset
MedWire News: Results from a Canadian study suggest that cognitive deficits are common at disease onset in patients with bipolar disorder (BD), and are therefore not wholly attributable to factors associated with disease duration.
"Patients with BD show broad cognitive impairments in sustained attention, memory, and executive functioning, not only during acute mood episodes but also during euthymic periods," say Lakshmi Yatham (University of British Columbia, Vancouver) and team.
However, they add that "little… is known about the presence or nature of cognitive impairment at the time of illness onset."
To investigate, the researchers studied 45 recently diagnosed BD patients who had recovered from a first episode of mania and 25 mentally healthy individuals (controls) who were matched for age, gender, education, ethnicity, and premorbid IQ.
All of the participants underwent neuropsychological tests to assess five key cognitive domains, including verbal/premorbid intellectual functioning, learning/memory, spatial/nonverbal reasoning, attention/processing speed, and executive function.
The researchers found that the BD patients exhibited significant impairments compared with controls in most of the cognitive domains assessed, including learning/memory, spatial/nonverbal reasoning, executive function, and some aspects of attention.
For example, patients scored significantly worse than controls in the California Verbal Learning Test trials (51.6 vs 58.7), the California Verbal Learning Test delayed recall (10.9 vs 12.7), Kaufman Brief Intelligence Test nonverbal (106.6 vs 113.4), FAS verbal fluency (38.5 vs 41.4), and special recognition (76.8 vs 83.2).
The researchers note in the Journal of Clinical Psychiatry that substance abuse problems, medication use, and residual mood symptoms did not fully explain the differences in cognitive function between the two groups.
Yatham and team conclude: "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."
They add: "These findings may provide etiologic clues into the illness and identify clinical targets for early treatment."
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By Mark Cowen