To our best knowledge, this study is the first fully epidemiological and largest [35–38] meta-analysis on age at onset of mental disorders globally. It also represents the most comprehensive approach, encompassing all ICD-11 diagnostic spectra for which we found eligible studies, allowing comparative transdiagnostic analyses across different categories of mental disorders [39, 40]. Furthermore, per protocol, high-quality population-level studies were included that are less likely to be affected by biases, meeting previous methodological recommendations [30]. Moreover, data from all continents of the world were available, providing global estimates on the age at onset of mental disorders. Importantly, the statistical approach of this meta-analysis provides an estimate of age at disorder onset distribution throughout the lifespan, going beyond mere centrality estimates.
