A new report to be published by The American Journal of Medicine shows that more than 60 percent of bankruptcy filings in the U.S. are due to overwhelming medical bills.

And it’s not just lack of insurance causing the problem. More than three quarters of the people who went under because of medical bills had private insurance.

“That was actually the predominant problem in patients in our study,” said lead author Steffie Woolhandler, M.D., of the Harvard Medical School. “Seventy eight percent of them had health insurance, but many of them were bankrupted anyway because there were gaps in their coverage like co-payments and deductibles and uncovered services. Other people had private insurance but got so sick that they lost their job and lost their insurance.”

According to the report, bankruptcies due to medical bills increased from 46 percent in 2001 to 62 percent in 2007. Most of those who filed for bankruptcy were middle-class, well-educated homeowners.

“Unless you’re a Warren Buffett or Bill Gates, you’re one illness away from financial ruin in this country,” Woolhandler said. “If an illness is long enough and expensive enough, private insurance offers very little protection against medical bankruptcy, and that’s the major finding in our study.”

According to Woolhandler, the number of medically related bankruptcies is probably worse than the report shows. The global economic meltdown and recession didn’t happen until a year after the study statistics were compiled.

An increasing number of Americans are dealing with out-of-control medical bills by shopping abroad for medical services. Many go to Mexico for their healthcare system, where national health plan coverage costs $250 a year.