Neuropsychological status of bipolar I disorder: impact of psychosis

Background The presence of schizotypal personality traits in some people with bipolar disorder, together with reports of greater cognitive dysfunction in patients with a history of psychotic features compared with patients without such a history, raises questions about the nosological relationship between bipolar disorder with psychotic features and bipolar disorder without psychotic features. Aims To test the impact of a history of DSM–IV-defined psychosis on the neuropsychological status of participants with bipolar disorder while statistically controlling for confounding factors such as mood, medication, alcohol misuse/dependence and childhood abuse, and to evaluate the impact of schizotypal personality traits (and thus potential vulnerability to psychotic illness) on the cognitive performance of people with bipolar disorder and their healthy relatives. Method Neuropsychological data were obtained for 25 participants with type I bipolar disorder and a history of psychosis, 24 with type I bipolar disorder but no history of psychosis and 61 unaffected relatives. Schizotypal traits were measured with the Schizotypal Personality Scale (STA). Childhood trauma was measured with the Childhood Trauma Questionnaire. Results The group with a history of psychosis performed significantly worse than the healthy relatives on measures of verbal working memory, cognitive flexibility and declarative memory. Nevertheless, the two bipolar disorder groups did not differ significantly from each other on any cognitive measure. Scores on the STA were negatively associated with verbal working and declarative memory, but positively associated with visual recall memory. Conclusions ‘Psychotic’ and ‘non-psychotic’ subtypes of bipolar disorder may lie on a nosological continuum that is most clearly defined by verbal memory impairment.