I'm not sure what to make of this study, which indicates that more than half of all personal bankruptcies were triggered by excessive medical costs, even though most of those debtors were covered by health insurance. There tend to be a multitude of reasons why people file, most notably mortgage defaults and exorbinant credit card debt, but high medical bills are invariably a part of the problem as well.
Practicing in Los Angeles, a region that has always been ahead of the curve when it comes to bankruptcy law, my perspective may not be applicable nationwide, but I can think of an obvious explanation as to why this study came to this conclusion. There is still a great deal of embarassment when it comes to the filing of bankruptcy. Psychologically, it is perceived as an admission of failure, an acknowledgement that you can't make good on your own promises. Thus, a good many people will try to postpone the inevitable, to be done only in extremis.
Of all the reasons to give in to the temptation of having a deus ex machina, in the form of the Bankruptcy Court, wipe your slate clean, a medical debt is probably the most appealing. We can't be blamed for getting sick, in the same way that we can feel blame for losing their job or running up too much credit card debt. High medical costs are as much a given in our society as having to pay through the teeth for housing or a sports car, but it's just easier to make believe that the medical debt was an arbitrary event, as opposed to the other big ticket items we couldn't afford but purchased anyway.