Background: Psychotic bipolar disorder may represent a neurobiologically distinct subgroup of bipolar affective illness. We sought to ascertain the profile of cognitive impairment in patients with bipolar disorder and to determine whether a distinct profile of cognitive deficits characterizes bipolar patients with a history of psychosis.
Methods: Sixty-nine outpatients with bipolar I disorder (34 with a history of psychotic symptoms and 35 with no history of psychosis) and 35 healthy comparison subjects underwent a comprehensive neurocognitive battery. All three groups were demographically matched.
Results: Despite preserved general intellectual function, bipolar I patients overall showed moderate impairments on tests of episodic memory and specific executive measures (average effect size = .58), and moderate to severe deficits on attentional and processing speed tasks (average effect size = .82). Bipolar I patients with a history of psychosis were impaired on measures of executive functioning and spatial working memory compared with bipolar patients without history of psychosis.
Conclusions: Psychotic bipolar disorder was associated with differential impairment on tasks requiring frontal/executive processing, suggesting that psychotic symptoms may have neural correlates that are at least partially independent of those associated with bipolar I disorder more generally. However, deficits in attention, psychomotor speed, and memory appear to be part of the broader disease phenotype in patients with bipolar disorder.