BACKGROUND: Research on basic self-disorders (BSD) has expanded since the introduction of the Examination of Anomalous Self-Experience (EASE). Although originally formulated as characterizing schizophrenia spectrum disorders, EASE-defined BSD have been reported in other psychiatric conditions and in individuals at clinical high-risk for psychosis (CHR-P), raising questions about their diagnostic specificity and their distribution across diagnostic categories. STUDY DESIGN: We conducted a Preferred Reporting Items for Systematic Reviews and Meta-Analyses- and Meta-analysis Of Observational Studies in Epidemiology-compliant meta-analysis of EASE studies in individuals with Diagnostic and Statistical Manual of Mental Disorders or International Classification of Diseases (DSM/ICD) mental disorders, CHR-P samples, and healthy controls. Random-effect meta-analyses examined weighted mean total and domain-specific EASE scores using binary and continuous scoring methods. Meta-regressions and sensitivity analyses assessed the distribution of BSD across 5 major diagnostic categories. STUDY RESULTS: Thirty-eight studies were included in the quantitative synthesis (n = 858/318 patients and n = 130/97 healthy controls for binary/continuous EASE scores, respectively). Meta-regressions indicated that diagnostic categories accounted for a substantial proportion of between-study variance in total EASE scores (QM(4) = 98.64, P < .001, R2 = 0.703). Schizophrenia spectrum disorders (k = 21) showed markedly higher scores compared to healthy controls (k = 4, P < .001), other mental disorders (k = 8, P < .001), non-schizophrenia spectrum psychosis (k = 4, P < .001), and CHR-P individuals (k = 10, P = .007). CHR-P samples exhibited intermediate BSD levels, higher than other mental disorders (P = .002) and non-schizophrenia spectrum psychosis (P = .041). CONCLUSIONS: EASE-defined BSD show a more pronounced concentration within schizophrenia spectrum conditions and are also elevated in CHR-P individuals. Nevertheless, some forms of BSD might be present in other psychiatric conditions. Further longitudinal and methodologically harmonized research is needed to better clarify the developmental trajectories and clinical significance of BSD across diagnostic categories.