>I skimmed a few papers and there's not a lot of rational behind the idea that vitamin deficiencies play a role in ADHD pathogenesis.

Isn't there some data showing correlation (not necessarily causation of course...people with poor self-regulation might have a poor diet for obvious commonsensical reasons) between low nutrient levels and ADHD?

Aren't nutrients implicated in all sorts of brain functions including ones related to mental-health issues, hence the burgeoning field of nutritional psychiatry?

What about the seemingly (to a layperson) straightforward experiment of just giving ADHD patients who are (e.g.) low in iron (or whatever) some iron and seeing if symptoms improve?