This is the first large-scale epidemiological meta-analysis that includes all available general population birth, cross-sectional and incidence studies investigating the age at onset of any ICD/DSM-mental disorders. Overall, the global onset of the first mental disorder occurs before age 14 in one-third of individuals, age 18 in almost half (48.4%), and before age 25 in half (62.5%), with a peak/median age at onset of 14.5/18 years across all mental disorders. However, there was significant variability in global age at onset and peak age across mental disorders. These findings can inform the timing and resource allocation regarding early intervention and preventive approaches.
