Pre-pulse inhibition deficits in individuals at clinical high-risk for psychosis: A systematic review and meta-analysis

Aim Neurophysiological markers of schizophrenia may help identify individuals who are at an increased risk of developing psychosis. As an operational measure of sensorimotor gating, pre-pulse inhibition (PPI) deficit has been investigated in clinical high-risk (CHR) individuals. In this study, we performed a systematic review and meta-analysis of studies that investigated PPI in CHR individuals. Methods Relevant studies published as of July 2019 were retrieved from the PubMed, Cochrane, Embase, PscyINFO, EBSCO and Chinese databases. PPI was evaluated by calculating the standard mean differences (SMDs) between CHR individuals and healthy controls (HC) in meta-analysis. Quality of studies was assessed using the Newcastle-Ottawa Scale.I(2)index was used to assess heterogeneity and Egger's test was used to assess publication bias. Results Eight studies were found to be eligible. The meta-analysis included five studies with a combined study population of 184 CHR subjects and 161 HC. CHR individuals showed lower PPI levels compared to HC in 120 ms inter-stimulus interval or stimulus onset asynchrony paradigm (P= .491, SMD = -0.62). No significant heterogeneity was observed in 120 ms PPI paradigm (chi(2)= 3.41,P= .491,I-2= 0.0%). Conclusion CHR individuals had lower PPI level compared to HC in 120 ms paradigm, which were relatively stable and significant. The results indicate the presence of information processing and inhibitory problems prior to the development of full-blown psychosis. PPI may be clinically used as an objective indicator to supplement the understanding of CHR individuals.