Correlates of cognitive deficits in first episode schizophrenia

The presence of cognitive dysfunction in schizophrenia has been well documented, but questions remain about whether there are relationships between this dysfunction and clinical symptomatology. If present, such relationships should be most clearly observable in patients with first episode schizophrenia; that is, before the effects of chronic illness, institutionalization, or treatment might confound them.

307 schizophrenia subjects in their first episode of illness were recruited to participate in a clinical trial comparing the long-term efficacy of haloperidol and risperidone. The psychopathology, cognitive functioning, early treatment history, and duration of untreated psychosis of these subjects were assessed prior to their assignment to randomized, double-blind treatment. Approximately two-thirds of the subjects were receiving antipsychotic treatment at the time of assessment; however, the duration of treatment was limited to 12 weeks or less.

The severity of negative symptoms at the time of assessment was associated with deficits in memory, verbal fluency, psychomotor speed and executive function. Positive symptoms were not associated with cognitive deficits. Also, the duration of untreated illness (DUI) prior to assessment was not significantly associated with cognitive impairment.

The results of this study of first episode schizophrenia patients suggest that a relationship exists between negative symptoms and cognitive dysfunction. However, that relationship accounts for only a minor portion of the variance (i.e., 10-15%) in the severity of cognitive dysfunction after controlling for a number of potentially confounding factors. This finding provides support for the theory that the neurobiological processes that give rise to symptomatology and cognitive dysfunction in schizophrenia are partially overlapping.