I have seen much written about B6 deficiency and OCD. You might want to google those two terms together.

I wonder, have they ever checked for gluten/casein or other food sensitivity in your nephew?

Given your brief description, I'd look further into both of these areas.

There is a Gluten Sensitivity/Celiac Disease forum here. If you nephew has an eating disorder and is a "picky" eater, please be sure he has been tested for guten sensitivity.

Good luck!

Cara