Purpose of the review
To review recent epidemiological research on age‐of‐onset (AOO) of mental disorders, focusing on the WHO World Mental Health (WMH) surveys.
Median and inter‐quartile range (IQR; 25th–75th percentiles) of AOO is much earlier for phobias (7–14, IQR: 4–20) and impulse‐control disorders (7–15, IQR: 4–35) than other anxiety disorders (25–53, IQR: 15–75), mood disorders (25–45, IQR: 17–65), and substance disorders (18–29, IQR: 16–43). Although less data exist for non‐affective psychosis, available evidence suggests that median AOO is in the range late teens through early 20s. Roughly half of all lifetime mental disorders in most studies start by the mid‐teens and three‐fourths by the mid‐20s. Later onsets are mostly secondary conditions. Severe disorders are typically preceded by less severe disorders that seldom are brought to clinical attention.
First onset of mental disorders usually occurs in childhood or adolescence, although treatment typically does not occur until a number of years later. Although interventions with early incipient disorders might help reduce severity‐persistence of primary disorders and prevent secondary disorders, additional research is needed on appropriate treatments for early incipient cases and on long‐term evaluation of the effects of early intervention on secondary prevention.
Keywords: Age of onset, prevention, early intervention, mental disorders, WHO World Mental Health (WMH) Survey Initiative