According to a poll earlier this year in the New England Journal of Medicine, a majority of American physicians say that single-payer is the best path forward. Doctors are not traditionally a progressive bunch — in the 1960s, the American Medical Association famously hired Ronald Reagan to attack Medicare as “socialized medicine.” So why might this be?

A new study exploring the phenomenon of physician burnout holds some clues. Researchers from University of California, Riverside School of Medicine found that under the current system, doctors are increasingly unhappy at work. They observed a sharp rise in physician burnout, which they define as “1) a feeling of a lack of accomplishment; 2) feelings of cynicism; and 3) a loss of zeal, zest, and enthusiasm for work.”

One of the reasons for this dissatisfaction is that, as researcher Kenneth A. Ballou pointed out, “the doctor-patient relationship has been morphed into an insurance company-client relationship that imposes limitations upon the treatment doctors can provide to the insurance company’s members.” In our current system, there are usually three parties involved in every medical decision: the doctor, the patient, and the insurer. The doctor and patient may agree on a course of treatment, but the insurer decides whether it will be covered. And since many Americans can’t afford ever-growing out-of-pocket medical costs, that often means that insurers have the final say in whether the treatment will be administered at all.