Neurocognitive impairments in individuals at ultra-high risk for psychosis: Who will really convert?

Impairments in neurocognitive function are considered as core features of schizophrenia. Individuals at ultra-high risk (UHR) for psychosis, the 'putative' prodrome of schizophrenia, generally show levels of impairments intermediate between schizophrenia patients and healthy controls. We investigated the neurocognitive performance of individuals at UHR for psychosis, comparing them with patients with first-episode schizophrenia (FES) and healthy controls (HC), and explored the predictivity of baseline neurocognitive function in the UHR group for transition to overt psychosis.

Individuals at UHR for psychosis (n = 60), patients with FES (n = 39), and HC subjects (n = 94) participated in the present study. All participants performed a comprehensive neurocognitive battery, consisting of tests for five separate neurocognitive domains (executive function, attention/working memory, processing speed, verbal memory, and spatial memory). UHR subjects were assessed for transition every month during 24 months of follow-up.

Neurocognitive performance in the UHR group was largely at intermediate levels. Attention/working memory and verbal memory were significantly different from both the FES and HC groups. In the UHR group, processing speed was decreased to the level of the FES group, while executive function and spatial memory were relatively preserved. In the Cox regression model, spatial memory significantly predicted the transition to overt psychosis in the UHR group.

The present study showed that neurocognitive impairments were evident in UHR individuals prior to the onset of overt psychosis. Our findings generally support the neurodevelopmental model of schizophrenia and suggest that there could be different developmental trajectories between converters and non-converters.