<jats:title>Abstract</jats:title><jats:sec><jats:title>Importance</jats:title><jats:p>The lack of robust neuroanatomical markers of psychosis risk has been traditionally attributed to heterogeneity. A complementary hypothesis is that variation in neuroanatomical measures in the majority of individuals at psychosis risk may be nested within the range observed in healthy individuals.</jats:p></jats:sec><jats:sec><jats:title>Objective</jats:title><jats:p>To quantify deviations from the normative range of neuroanatomical variation in individuals at clinical high-risk for psychosis (CHR-P) and evaluate their overlap with healthy variation and their association with positive symptoms, cognition, and conversion to a psychotic disorder.</jats:p></jats:sec><jats:sec><jats:title>Design, Setting, and Participants</jats:title><jats:p>Clinical, IQ and FreeSurfer-derived regional measures of cortical thickness (CT), cortical surface area (SA), and subcortical volume (SV) from 1,340 CHR-P individuals [47.09% female; mean age: 20.75 (4.74) years] and 1,237 healthy individuals [44.70% female; mean age: 22.32 (4.95) years] from 29 international sites participating in the ENIGMA Clinical High Risk for Psychosis Working Group.</jats:p></jats:sec><jats:sec><jats:title>Main Outcomes and Measures</jats:title><jats:p>For each regional morphometric measure, z-scores were computed that index the degree of deviation from the normative means of that measure in a healthy reference population (N=37,407). Average deviation scores (ADS) for CT, SA, SV, and globally across all measures (G) were generated by averaging the respective regional z-scores. Regression analyses were used to quantify the association of deviation scores with clinical severity and cognition and two-proportion z-tests to identify case-control differences in the proportion of individuals with infranormal (z<-1.96) or supranormal (z>1.96) scores.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>CHR-P and healthy individuals overlapped in the distributions of the observed values, regional z-scores, and all ADS vales. The proportion of CHR-P individuals with infranormal or supranormal values in any metric was low (<12%) and similar to that of healthy individuals. CHR-P individuals who converted to psychosis compared to those who did not convert had a higher percentage of infranormal values in temporal regions (5-7% vs 0.9-1.4%). In the CHR-P group, only the ADS<jats:sub>SA</jats:sub>showed significant but weak associations (|β|<0.09; P<jats:sub>FDR</jats:sub><0.05) with positive symptoms and IQ.</jats:p></jats:sec><jats:sec><jats:title>Conclusions and Relevance</jats:title><jats:p>The study findings challenge the usefulness of macroscale neuromorphometric measures as diagnostic biomarkers of psychosis risk and suggest that such measures do not provide an adequate explanation for psychosis risk.</jats:p></jats:sec><jats:sec><jats:title>Key points</jats:title><jats:sec><jats:title>Question</jats:title><jats:p>Is the risk of psychosis associated with brain morphometric changes that deviate significantly from healthy variation?</jats:p></jats:sec><jats:sec><jats:title>Findings</jats:title><jats:p>In this study of 1340 individuals high-risk for psychosis (CHR-P) and 1237 healthy participants, individual-level variation in macroscale neuromorphometric measures of the CHR-P group was largely nested within healthy variation and was not associated with the severity of positive psychotic symptoms or conversion to a psychotic disorder.</jats:p></jats:sec><jats:sec><jats:title>Meaning</jats:title><jats:p>The findings suggest the macroscale neuromorphometric measures have limited utility as diagnostic biomarkers of psychosis risk.</jats:p></jats:sec></jats:sec>