Hippocampal volume in subjects at clinical high-risk for psychosis: A systematic review and meta-analysis.

•Magnetic resonance imaging studies of hippocampal volume in clinical high risk patients compared to healthy controls.•Clinical high risk patients showed no hippocampal volume reduction.•Hippocampal volume cannot be used as a biomarker.•This meta-analysis fosters the neurodegenerative hypothesis of hippocampal volume reduction around transition to psychosis.