My uncle Bill was one of those guys with "too much energy". Among other things, starting at age 10 he would climb out his bedroom window at 1 in the morning, walk on the train tricks to the city ten miles away, and be back in bed before dawn. My grandparents only found out about his nightly forays when the police found him outside at 3 a.m. What's odd is that I've heard of several others engaging in this exact same behavior - sneaking out at night to follow train tracks or paths.
This level of restlessness doesn't necessarily require a diagnosis but the repeated pattern is still striking. You can't help but wonder what gives some people this kind of energy and why it expresses itself in terms of "exploratory" behavior. One possibility is that these individuals are acting out behaviors which were adaptive at one time, and that in fact these are goal-less random walks of the sort that predators engage in to find new hunting territory. That I know of, none of these individuals were diagnosed ADHD, but it certainly brings to mind the hunter-farmer theory. It would be very interesting to genotype these individuals for DRD4 polymorphisms, since a) there are DRD4 alleles associated with ADHD (7R) and b) in one African population split between farmers and nomads, the 7R allele was associated with greater stature and weight in nomads, but not in sedentary farmers.
The next step is to look at behavioral correlates of the DRD4 allele. In particular:
1) Ability to tolerate pain or negative stimuli while pursuing a goal, DRD47R vs non-7R. This may be a way to measure the lay term "hyperfocus", to see if it's real and if so, how and to what extent it manifests in 7Rs.
2) Comparative activity of reward circuity in DRD47Rs to non-7Rs, perhaps by fMRI. An fMRI study has already been done correlating 7R, reward circuity activation from food, and weight gain.
Of interest to readers mostly for humor: I already know from an ethnic genotyping study that I have a DRD1 mutation, and although it was novel at the time to the big databases, it was in the middle of an intron so it probably has no effect. But I haven't yet been sequenced at my other receptors and plan two within the next two years. I would put good money on having at least one 7R. Given the greater food rewards, this only supports my argument that people with good manners just don't like food.