A recent study confirms the validity of the DSM-5 change to the age of onset criterion for diagnosis of attention-deficit/hyperactivity disorder (ADHD). In DSM-5, age of onset criterion for ADHD, previously set at 7 in DSM-IV, has been raised to 12. As explained in DSM-5, age of onset is now set at 12, rather than an earlier age, to reflect the importance of clinical presentation during childhood for accurate diagnosis, while also acknowledging the difficulties in establishing precise childhood onset retrospectively.

Source: Validity of change in DSM-5 attenti... (ADHD) age of onset criterion confirmed