A longitudinal study of neurocognitive function in individuals at-risk for psychosis

Clinically defined prodromal diagnostic criteria identify at-risk individuals with a 35-40% likelihood of developing a psychotic disorder within a year. The time course and predictive value of cognitive deficits in the development of psychosis has not been established.

A comprehensive neurocognitive battery and clinical assessments were administered to 37 subjects meeting Criteria of Prodromal States (COPS) criteria for being at risk for psychosis, and two comparison groups: 59 first episode and 47 healthy subjects. Subjects were also evaluated at 6-month and 1-year follow-up periods. Primary analyses used a neurocognitive composite score derived from individual neurocognitive measures, including measures of vigilance, verbal memory, working memory, and processing speed.

At-risk subjects performed more poorly than healthy subjects (t=2.93, P=0.01), but better than first episode subjects (t=4.72, p<0.0001). At-risk subjects were particularly impaired on measures of vigilance and processing speed. Cognitive composite scores were significantly lower in at-risk subjects who progressed to psychosis (N=11; z=-1.2), while those at-risk subjects who did not progress to psychosis (N=17) performed better (z=-0.5), and not significantly different from controls. Poor CPT performance combined with better WAIS-R digit symbol performance predicted progression to psychosis. Severity of neurocognitive deficits was not related to duration of prodrome or to time to development of psychosis and neurocognitive function improved in all subjects except those who progressed to psychosis.

Neurocognitive impairment emerges early in the course of psychotic illness. Performance on tests of neurocognition may prove to be an early risk predictor for subsequent development of psychotic disorders.