Neuropsychology of the prodrome to psychosis in the NAPLS consortium: relationship to family history and conversion to psychosis

Abstract

Context: Early detection and prospective evaluation of clinical high-risk (CHR) individuals who may develop schizophrenia or other psychotic disorders is critical for predicting psychosis onset and for testing preventive interventions.

Objectives: To elucidate the neuropsychology of the CHR syndrome, to determine the association of neuropsychological function with conversion to psychosis and family history of psychosis, and to examine whether baseline neuropsychological functioning predicts subsequent psychosis.

Design: Longitudinal study with 2(1/2) years of follow-up.

Setting: Eight centers participating in the North American Prodrome Longitudinal Study.

Participants: Three hundred four prospectively identified CHR individuals meeting Structured Interview for Prodromal Syndromes criteria, 52 non-CHR persons with a family history of psychosis in first- or second-degree relatives (family high-risk group), and 193 normal controls with neither a family history of psychosis nor a CHR syndrome, all of whom underwent baseline neuropsychological evaluations.

Main outcome measures: A neurocognitive composite score, 8 individual neuropsychological measures, an IQ estimate, and high-risk status.

Results: Global ("composite") neuropsychological functioning was comparably impaired in the CHR and family high-risk groups compared with controls, but profiles differed significantly between groups. Neuropsychological functioning in the CHR group was significantly lower in persons who progressed to psychosis than in those who did not and was worst in the subgroup with a family history of psychosis. Tests of processing speed and verbal learning and memory were most sensitive in discriminating CHR individuals from controls, although reductions were less severe than in established schizophrenia. Neuropsychological functioning did not contribute uniquely to the prediction of psychosis beyond clinical criteria, but worse verbal memory predicted more rapid conversion.

Conclusions: These findings document that CHR individuals have significant neuropsychological difficulties, particularly those who later develop psychosis. This dysfunction is generally of moderate severity but less than in first-episode schizophrenia, suggesting that further decline may occur after baseline CHR assessment.

Figure 1

Neuropsychological Profiles of CHR (Total Sample), CHR Converters, CHR Non-Converters, and FHR Groups Standardized Against the Normal Control Group from the “Multivariate” Sample

Figure 2

Effect Sizes (ES) reflecting comparisons of different High Risk groups with normal controls. ESs (Cohen’s d) are averaged within group in the “Univariate” sample after weighting for sample size across the 8 neuropsychological test variables. Data suggests a dose response impact of both conversion and family history of psychosis. Comparisons are as follows (average number of subjects per test per group in parenthesis: NC (n= 144): 1) CHR Non-Converters (n=155); 2) CHR (total sample [n=242]); 3) FHR (n=45); 4) CHR Converters (n=62); 5) CHR Converters/FH+ (n=13).