I was reading this blog in which a mother discusses her son eating from the litterbox. Sounds like the kind of thing I would have done, if we'd had cats when I was that age. (I was more into sticking forks into electrical outlets. Really.)
General loss of appetite
"Yuck. Yuck, yuck, yuck. I have just washed Valli's mouth out, along with his little hands and face, after finding him eating out of the cat litter box. He proudly announced that he was eating sand! Eeeouw! So gross; I don't think I'll eat that delicious Indian curry that Jón is making, my stomach is still churning."