I don't know anything about chiropractics and even less about ADHD . . . but in terms of practitioners there's also osteopathy. I think osteopaths and chiropracters have very different training and are licensed/regulated differently.

I go to an osteopath for alignment issues related to a back injury, and I know my doc has a number of patients who are kids and dealing with some chronic issue . . . I guess the theory is that osteopathic treatment might help the body's natural healing mechanisms? I've never really asked about it.

Just another type of doc you might want to look into . . .