Here's the best article I've read so far about Michael Jackson's chronic pain and drug addictions:
Those body image problems aside, Pinsky said the most serious problem with opiate addiction is that the drugs themselves can cause pain when the patient begins to feel that if they cease taking the medication they will be in even worse agony. "With chronic pain, once you start taking these medications, you are in constant pain," Pinsky said. "And when you have enablers around you who help provide the drugs, it makes it almost impossible to get off of them. It's like a crack addict living in a crackhouse." ...
"You get to the point where you build up such a high tolerance to the opiates that you can't take enough to get the desired effect, or enough to keep you from painful withdrawal," said Dr. Arnold M. Washton, a New York-based psychologist with more than 30 years of expertise in treating addiction. "And chronic use makes it impossible to go to sleep, so the person using these drugs may use double or triple the dose, hoping to go to sleep, but no matter how much they use, they can't. So they need to switch to a drug that affects a different part of the brain, which are the sedative drugs."
Scary stuff. These kinds of stories are why I'm so hesitant to follow the libertarian road to total drug deregulation.