Course of neurocognitive deficits in the prodrome and first episode of schizophrenia

Abstract

Understanding the trajectory of cognitive changes in the development of schizophrenia may shed light on the neurodevelopmental processes in the beginning stage of illness. Subjects at risk for psychosis (AR, n = 48), patients in their first episode of schizophrenia (FE, n = 20), and normal comparison subjects (n = 29) were assessed on a neurocognitive battery at baseline and at a 6-month follow-up. There were significant group differences across all cognitive domains as well as a significant group by time interaction in the verbal learning domain. After statistically controlling for practice effects and regression to the mean, a high proportion of FE subjects showed an improvement in verbal learning, and a significant number of AR subjects improved in general intelligence. Moreover, a higher than expected percentage of FE subjects, as well as AR subjects who later converted to psychosis, showed a deterioration in working memory and processing speed. These inconsistent trajectories suggest that some domains may improve with stabilization in the early stages of psychosis, whereas others may decline with progression of the illness, indicating possible targets for cognitive remediation strategies and candidate vulnerability markers for future psychosis.

Figure 1

Mean z-score differences (follow-up – baseline) and standard errors for each group. The higher the difference score, the better the performance at follow-up. EF = executive functioning; PS = processing speed; VL = verbal learning; WM = working memory; IQ = general intelligence; GNI = global neurocognitive index.

Figure 2

Overall neurocognitive performance, as measured by the global neurocognitive index, at baseline and follow-up for each group. The bars represent the standard errors.

Figure 3

Pattern of performance over time and across domains for each group, including the subgroup of at-risk subjects who converted to psychosis and the one who did not. EF = executive functioning; PS = processing speed; VL = verbal learning; WM = working memory; IQ = general intelligence; GNI = global neurocognitive index; 1 = baseline; 2 = follow-up. The bars represent the standard errors.