Objectives: Structural brain magnetic resonance imaging studies of individuals at ultra-high risk (UHR) for psychosis have shown subtle but widespread reductions in baseline gray matter volume (GMV) in the frontal, temporal, and limbic regions compared with healthy controls (HC). These regions coincide with regions of reduced GMV in patients with established psychosis and have led to the consideration of structural changes in UHR as a potential biomarker for future transition to psychosis. However, most studies have been from Europe, North America, and Australia, with few reports from other regions, and two recent studies from Asian countries have failed to detect regional GMV reduction in UHR, suggesting the need for further analysis of an Asian sample. In this study, we investigated GMV reduction in Japanese UHR subjects. Results: The study used voxel-based morphometry to compare magnetic resonance imaging brain scans between 45 UHR individuals recruited by a specialist and 33 HCs. This showed no significant GMV reduction in the UHR group compared with the healthy control group. This negative result may be attributable to characteristics of Asian samples, such as a low prevalence of illicit drug use, or to the heterogeneous nature of UHR subjects.
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