P50 suppression in individuals at risk for schizophrenia: the convergence of clinical, familial, and vulnerability marker risk assessment.

Background: Identification of individuals at risk for the development of schizophrenia is important because it can lead to a greater understanding of the early stages of the illness. The aim of the present study was to determine whether individuals "at risk" for schizophrenia have deficits in P50 suppression, a preattentive measure of sensory gating.

Methods: Thirty-one at-risk and 21 normal comparison subjects were referred to the CARE (Cognitive Assessment and Risk Evaluation) Program at University of California San Diego. The primary aim of the CARE Program is to identify individuals who are at the greatest risk for conversion to psychosis, with a combination of clinical, familial, and vulnerability markers, including P50 suppression.

Results: As a group, the at-risk subjects had modestly lower levels (effect size=.43) of P50 suppression (55.1%, SD=39.8) relative to comparison subjects (71.5%, SD=34.7). At-risk subjects with a first-degree relative with schizophrenia had profoundly deficient P50 suppression (16.4%, SD=33.8) compared with other at-risk (p<.05) and comparison subjects (p<.005).

Conclusions: Ongoing longitudinal follow-up studies will determine whether it is possible to improve the predictive validity of the clinical and familial variables by using P50 suppression alone or in combination with other measures in determining which individuals are at greatest risk for schizophrenia.