What's Ozzy Osbourne's problem?

Although he has clearly been one of rock's many poster boys for self-destructive behavior (along with Keith Richards and Lemmy Kilmister, just to name a few), from what I gather the difficulty moving and speaking, along with the Parkinsons-like symptoms (though he doesn't in fact have Parkinson's) is in large part due not to his past substance abuse but to genes. I believe the "Behind the Music" episode about him mentioned something about some of those symptoms running in his family, despite the fact that his parents and siblings didn't share his "excess and debauchery" lifestyle.