That's not really true, or at least it would be hard to say for sure. Every source saying that cites the same survey where a majority of respondents claimed that it was at least a contributing factor. Its actually really hard to get good breakdowns of the numbers on this.

It's sort of a straw that breaks the camel's back situation in most cases I would wager. It's less that medical debt caused bankruptcy than it, added on top of housing debt and car loans and credit cards and student loans etc., finally pushed a household to a point where getting out from under it all was too much.

Yeah, I don’t exactly disagree. Many years ago I worked at a debt counseling company and had occasion to look at the records and listen in on phone calls. It was really quite fascinating and heartbreaking. There definitely seemed to be a few common patterns. Big debts around car crashes and complicated births were not uncommon. But on the other hand almost everyone had a crazy mortgage and a pile of credit card debt too.