Well yes and no, some people have serious issues, the next time u watch an episode watch the persons face when they do their "addiction" like, that one episode where the girl eats toilet paper, watch her face when she eats it.
No sadly. Not always. There are mental disturbances that can cause such things. Pica, eating non-edible things, is fairly common. Its a type of OCD i believe. Many of those wierd obsessions stem from true OCD and anxiety disorders that can very easily take over someones life.