History of psychosis and previous episodes as potential explanatory factors for neurocognitive impairment in first-treatment bipolar I disorder.

OBJECTIVES: Explanatory factors for the observed neurocognitive impairment in early-stage bipolar I disorder (BD-I) have received little attention. The current study investigated neurocognitive functioning in first-treatment (FT) BD-I compared to FT schizophrenia (SCZ), and healthy controls (HCs), and the effect of history of psychosis and previous episodes in the two clinical groups.

METHODS: A total of 202 FT patients with BD-I (n = 101) and SCZ spectrum disorder (n = 101), in addition to HCs (n = 101), were included. A comprehensive neurocognitive test battery was used to assess verbal learning and memory, executive functioning, processing speed, and attention and working memory. Neurocognitive functioning and the effect of history of psychosis and number of previous episodes were analyzed using separate multivariate analyses of variance and correlation analysis.

RESULTS: FT patients with BD-I performed intermediately between FT SCZ spectrum patients and HCs on all measures. Compared to HCs, FT BD-I showed impaired functioning across all neurocognitive domains. No differences in neurocognitive functioning were observed in psychotic versus nonpsychotic FT patients with BD-I. With the exception of an association between number of manic episodes and two measures of executive function in FT BD-I, no associations were found between number of episodes and neurocognitive performance.

CONCLUSIONS: Neurocognitive impairments were present in FT BD-I, and were not explained by history of psychosis or number of previous psychotic or depressive episodes. There were indications that executive function could be associated with number of previous manic episodes.