A comparative profile analysis of neuropsychological functioning in patients with schizophrenia and bipolar psychoses

Evidence for neuropsychological deficits in schizophrenia is substantial whereas evidence for the specificity of dysfunction is relatively sparse. To assess specificity, we compared neuropsychological function in patients with chronic schizophrenia, patients with chronic psychotic bipolar disorder and normal controls. Groups were comparable on age, ethnicity and expected intellectual ability (based on single word reading). Patients with schizophrenia and bipolar psychoses were also relatively similar on age at onset and number of hospitalizations. Using multivariate analyses of variance with sex and parental SES as covariates (our primary analyses), patients with schizophrenia were significantly more impaired than controls on seven of eight neuropsychological functions (all but verbal ability), and were significantly more impaired than bipolar patients on abstraction, perceptual-motor speed and vigilance. Bipolar patients were significantly impaired compared to controls on declarative verbal memory, and showed moderate-to-large effect size decrements on abstraction, perceptual-motor speed and vigilance. Results were not attenuated when IQ was controlled, which was significantly lower in patients with schizophrenia. Analyses indicated that the two psychiatric groups had similar profile patterns, but that patients with schizophrenia had a more severe impairment than patients with bipolar psychoses. Further research is required to determine whether similar mechanisms underly the neurocognitive deficits in these disorders.