Beware of iffy-seeming stats:  An interview with Charles Seife, author of Proofiness: The Dark Arts of Mathematical Deception.

The issue is that in medicine or any other field of study, it’s really easy to show that two things are linked in some manner…A number of years ago there was a study that showed the higher your credit card debt, the worse your health. The conclusion seemed to be “Don’t carry a balance on your credit card, otherwise you’ll get sick.” It’s probably just the opposite. People who are sick are running up medical bills, missing work or maybe have lost their jobs. It’s not that credit cards cause bad health. It’s that bad health causes unpaid bills on your credit card.