Incidentally, the response of somebody with ADD to Adderall is completely different compared to response of a normal person to amphetamines. It is more like "relaxed concentration" than stimulation.
Therapeutic dose of Adderall is way smaller than "recreational" doses of amphetamine. It has to be carefully calibrated by therapist. Higher doses will lead to headaches and, paradoxically, tiredness and drowsiness — not stimulation.