I don't know if this is fact or myth because I am not ADHD however, I was told caffeine and/or stimulants "relax" those who are dx.

I can see an instant change in my son's behavior when he is on meds and he describes it as numeral messages constructing thoughts in his mind are quieted just to the ones he wants to focus and concentrate on. Without meds, he says he has difficulty concentrating very long on one particular task especially if it is boring.