Oh true, I studied ADHD a bit, it's a neuro-developmental disorder of the dopaminergic system. Specifically, the motor cortex will develop more quickly/strongly than the executive function system, leading to a hyperactivity of motor activity and a hypo*activity of the "secretary" of the mind which filters/prioritizes/plans behaviors. Now there is a subset of primarily inattentive ADHD, which has less to do with movement and more to do with "spacing out" and lack of focus/attention, which can be combined with hyperactivity in the combined type (CT), versus the primarily inattentive subtype (PI). Also, yes, those with ADHD are much more likely to abuse stimulants, marijuana, and alcohol, anything with which to alter the brain chemistry away from a normal modality which might be stressful to be in. I have heard anecdotal tales about ADHD medications as revelations bordering on spirituality, people crying after taking their first dose at age 30 and realizing how much more "normal" it might make them. Really good to know that people can react so positively, though we also know that many non-ADHD individuals abuse the drugs as well.