I'm also an adult difficult child and other than caffeine making my anxiety much worse and excessive chocolate giving me severe headaches; I've never noticed any effect on my moods from my diet.
I do know that many people have had good results from gluten/casein free diets and while I do avoid artificial dyes and high fructose corn syrup, other than that I can't say that any special diets have helped.
If you post on the natural section, there are several people there who can further advise you.
