Objectives: Neurocognitive dysfunction is likely to represent a trait characteristic of bipolar disorder, but the extent to which it comprises 'core' deficits as opposed to those secondary to longstanding illness or intellectual decline is unclear. We investigated neuropsychological performance in an epidemiologically derived sample of patients with a first affective episode with psychotic symptoms and a positive history of mania, compared to community controls.
Methods: Using a nested case-control, population-based study, measures of episodic and working memory, executive function, processing speed, and visual-spatial perception were compared between 35 patients with a first affective episode with psychotic symptoms and a positive history of mania, and 274 community controls, as well as a subgroup of 105 controls matched on current IQ ('good' versus 'poor') and IQ trajectory ('stable', 'declined', or 'improved') with the patients (three controls per case).
Results: Compared to the extended control sample, probands showed a suggestive deficit in short-term verbal recall, and a significant deficit in semantic fluency. Only the latter was detectable in the comparison with the IQ-matched controls. All other neurocognitive domains showed intact performance or nonsignificant deficits of small effect sizes compared to both control groups. Semantic fluency showed no association with symptoms or duration of untreated illness.
Conclusions: Patients with a first affective episode with psychotic symptoms and a positive history of mania show an isolated, selective deficit in semantic verbal fluency, against a background of generally preserved neurocognitive function. This pattern seems to contrast with the more widespread neuropsychological dysfunction seen in schizophrenia.