Solmi M, Radua J, Olivola M, et al. - Researchers sought to report robust, global epidemiological estimates of age at onset for mental disorders. A PRISMA/MOOSE-compliant systematic review with meta-analysis was conducted of birth cohort/cross-sectional/cohort studies, representative of the general population, describing age at onset for any ICD/DSM-mental disorders, incorporated in PubMed/Web of Science (up to May 16, 2020). Across 192 included studies (n = 708,561), the proportion of individuals with onset of any mental disorders before the ages of 14, 18, 25 were 34.6%, 48.4% and 62.5%, respectively; 14.5 years was reported to be the peak age. For diagnostic blocks, the following estimates of proportion of individuals with onset of disorder before the age of 14, 18, 25 and peak age were generated: neurodevelopmental disorders: 61.5%, 83.2%, 95.8%, 5.5 years; anxiety/fear-related disorders: 38.1%, 51.8%, 73.3%, 5.5 years; obsessive-compulsive/related disorders: 24.6%, 45.1%, 64.0%, 14.5 years; feeding/eating disorders/problems: 15.8%, 48.1%, 82.4%, 15.5 years; conditions specifically associated with stress disorders: 16.9%, 27.6%, 43.1%, 15.5 years; substance use disorders/addictive behaviors: 2.9%, 15.2%, 48.8%, 19.5 years; schizophrenia-spectrum disorders/primary psychotic states: 3%, 12.3%, 47.8%, 20.5 years; personality disorders/related traits: 1.9%, 9.6%, 47.7%, 20.5 years; and mood disorders: 2.5%, 11.5%, 34.5%, 20.5 years. The results provide insight into the timing of good mental health promotion/preventive/early intervention, and may aid in updating the current mental health system structured around a child/adult service schism at age 18.