Adderall treats ADHD in children as young as 3 years old, and it can be used in adults as well. It can also treat narcolepsy in people who are at least 12 years old. Doctors will start you at the lowest possible effective dose. You can build a tolerance to Adderall, so it may not work the same over time. You will gradually receive higher doses, depending on how you respond to Adderall.