How long does it take to outgrow adhd?

Varies . Prospective studies (research done over long periods following the same patients) show about 65% of children with add persist into adulthood. This number drops to 35% if the child is treated with stimulant medication. So to increase your chances of "outgrowing" adhd, treat early in childhood.
Variable. About 50% of people with childhood ADHD will out grow their symptoms by the end of high school. For others, it will be a life long issue.
Not everyone... ...Outgrows it. Some adults and even seniors have it, too.