Thanks to Obamacare, America’s corps of doctors appears to have a case of the blues.

The Physicians Foundation recently asked more than 13,000 doctors about their morale, their career plans, their practices, and their views of Obamacare. The results were grim.

Nearly six in 10 doctors said that they are less positive about the future of health care in America under Obamacare. Almost two-thirds have a negative attitude toward their jobs — nearly twice as many as before Obamacare passed.

As a result, many doctors are cutting back on their workload or shuttering their practices altogether. Worse, their collective frustration is exacerbating our nation’s troubling doctor shortage.

More than three-fifths of doctors say they would retire today if they could, compared with 45 percent before Obamacare. Eighty-four percent say the medical profession is in decline. Fewer doctors say they would enter the profession today if they had it to do over again, and fewer would recommend it to their children.

This decline in doctors’ morale is taking a toll on Americans’ ability to access care. Physicians report working almost 6 percent fewer hours than they did four years ago. That’s about two and a half hours less per week per doctor. Add up all the hours, and it’s the equivalent of losing more than 44,000 full-time physicians.

Doctors also report seeing some 16 percent fewer patients than they did in 2008. That represents tens of millions fewer doctor-patient encounters each year.

More than half of those surveyed say they plan to cut back further on the time they devote to patient care, to work part time, to retire, or to switch to direct-pay “concierge”-type medical practices, which are beyond the reach of many of Obamacare’s rules and regulations.

Even before Obamacare became law, America faced a chronic doctor shortage, with a gap of 14,000 physicians in 2010. And the problem will only grow worse.

According to the Association of American Medical Colleges, Obamacare will push the doctor shortage up to 63,000 by 2015 — and more than 91,000 by 2020. That’s in addition to the full-time-equivalent losses from doctors working fewer hours.

Obamacare’s $716 billion worth of cuts to Medicare are partially to blame. The law creates an “Independent Payment Advisory Board” charged with restraining the growth of Medicare spending. The board may not ration care or reduce seniors’ benefits — so its only real option for reducing spending will be cutting reimbursement rates for healthcare providers who treat Medicare patients. And that will discourage doctors from seeing them.

A 2010 survey by the American Medical Association found that nearly a third of primary care physicians already restrict the number of Medicare patients they accept because of low reimbursement rates. This year’s Physicians Foundation survey found that it’s grown even harder for seniors to find a doctor, as more than half of physicians currently limit the number of Medicare patients they’ll accept — or plan to do so.

For the low-income folks covered by Medicaid, securing a doctor’s appointment is even more difficult. Fewer than half of primary care doctors take on new Medicaid patients, for whom reimbursement rates are lower than in Medicare.

And again, Obamacare will only make things worse. The healthcare law will expand Medicaid coverage to some seven million additional people by 2014. These folks may be newly insured — but they likely won’t be able to see a doctor.

When he stumped for healthcare reform three years ago, President Obama said that doctors would be the best judge of his efforts because they “know the health care system best.”

He was certainly right about that. And by quitting the profession in droves, their verdict is in. It’s high time to pull the plug on a law that is already exacerbating America’s shortage of doctors — and may deprive Americans of adequate access to health care.

Sally C. Pipes is president and Taube Fellow in Health Care Studies at the Pacific Research Institute.