Around 40% of the more than $1 trillion in outstanding student loans went to financing graduate and professional degrees, the study found. Combined debt levels of the average graduate borrower, according to the study, have surged by $17,000 — from $40,000 in 2004 to more than $57,000 in 2012, adjusted for inflation. For the average undergraduate borrower, that increase was just $7,580, according to separate New America Foundation report.

While the higher debt level is more manageable for medical school student, for instance, it could be crippling for Master of Arts students, among whom the median debt is $58,000.

Some of the study’s more eye-popping statistics pertained to law school students, whose job prospects are famously declining. The level of indebtedness for this group rose by more than $50,000 from 2008 to 2012, with the typical law student now owing $140,000, the study found — a jump that’s unprecedented in any other field, including medicine.

“Most of these degrees are not intuitively worth it. They’re not gateways to the middle class,” says Jason Delisle, the study’s author. “Is a Master of Arts degree really worth $20,000 more than it was in 2004?”