Context: A substantial proportion of people at clinical high risk (HR) of psychosis will develop a psychotic disorder over time. Cognitive deficits may predate the onset of psychosis and may be useful as markers of increased vulnerability to illness.
Objective: To quantitatively examine the cognitive functioning in subjects at HR in the literature to date.
Data sources: Electronic databases were searched until January 2011. All studies reporting cognitive performance in HR subjects were retrieved.
Study selection: Nineteen studies met the inclusion criteria, comprising a total of 1188 HR subjects and 1029 controls.
Data extraction: Neurocognitive functioning and social cognition as well as demographic, clinical, and methodological variables were extracted from each publication or obtained directly from its authors.
Data synthesis: Subjects at HR were impaired relative to controls on tests of general intelligence, executive function, verbal and visual memory, verbal fluency, attention and working memory, and social cognition. Processing speed domain was also affected, although the difference was not statistically significant. Later transition to psychosis was associated with even more marked deficits in the verbal fluency and memory domains. The studies included reported relatively homogeneous findings. There was no publication bias and a sensitivity analysis confirmed the robustness of the core results.
Conclusions: The HR state for psychosis is associated with significant and widespread impairments in neurocognitive functioning and social cognition. Subsequent transition to psychosis is particularly associated with deficits in verbal fluency and memory functioning.