For people who had been awaiting the rollout of the Affordable Care Act in order to obtain health insurance for the first time, the major problem associated with American healthcare has been a lack of access to it. But for a surprising number of Americans, the greater problem may be exactly the opposite: They are receiving too much healthcare. And that’s not good news for either their wallets or their physical well-being.

The most recent estimate from the Institute of Medicine is that about 30 percent of total healthcare expenditures in America go toward unneeded care. Doctors, too, have acknowledged the problem: In a 2011 survey published in the Archives of Internal Medicine, 42 percent of American primary care physicians said that patients in their own practice were getting more care than necessary.

Excessive care typically takes the form of overabundant referrals to specialists, more diagnostic tests than would be medically necessary, or too many prescriptions—but in some cases, it can extend to actual treatments or surgeries that are not clinically indicated. Richard Baron, president of the American Board of Internal Medicine, is candid about the problem. “There were and are lots of things being done in healthcare that don’t reliably benefit patients,” he says.

From a patient perspective, it can be hard to see at first glance how too much care could be a problem. What’s wrong with an extra test, just to be safe? That almost sounds like a good thing.

But unneeded healthcare can be physically damaging. “Anything we do in medicine and healthcare has expected benefits and harms,” says Brenda Sirovich, a research associate at the VA Medical Center in White River Junction, Vermont, and the lead researcher behind the physician survey mentioned earlier. “Any time you have an intervention for a patient, no matter how small […] there is also the chance that it’s going to do some harm.” She points to the example of CT scans: for patients who are genuinely sick, they’re an important diagnostic tool. But they also expose patients to radiation, and when used too liberally, their harms outweigh their benefits.

Even for initial screening tests that pose no risk in themselves, there’s the problem of the “downstream effect;” if the first test produces an ambiguous result or a false positive, it can lead to more invasive testing that does carry substantial risk. “As you intervene on patients who have less and less reason to intervene and less and less chance of benefiting, you still retain that probability of harming them,” says Sirovich. “In a word, that is the biggest problem with doing too much—the risk of harm.”

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In some cases, the roots of the excess care are noble: Doctors just want to provide the best possible care for their patients. The operating assumption for many both inside and outside the medical field tends to be that if a little care does a little good, a lot of care will do a lot of good. Given the time constraints that many physicians are under, it can seem safest to default to over-ordering.

But there are several other major drivers of overutilization, as well. Experts debate exactly how much the threat of lawsuits influences physicians in their practice of medicine, but physicians themselves say that fear of legal challenges is a substantial factor in motivating them to provide too much care. (In Sirovich’s physician survey, malpractice was cited far more frequently than any other factor as incentivizing physicians to do more than they felt was clinically necessary.)

Skeptics challenge that physicians might not be in the best position to know exactly what motivates their own behavior. But a study published in Health Affairs this summer suggests that the malpractice effect is real. According to the report, doctors who acknowledge having a strong fear of malpractice are more likely to show a pattern of ordering aggressive diagnostic tests, and they’re also more likely to refer patients to the ER for treatment. This makes intuitive sense: Doctors are rarely asked if they did too much, but they are constantly questioned as to whether or not they did enough—and they know they can wind up in legal trouble if patients don’t think their care was sufficient.

Perhaps more troubling than medical liability issues are the financial incentives inherent in the American healthcare system. Most American healthcare currently operates on a fee-for-service model, where physicians receive payment for every service performed, regardless of whether that service actually benefits the patient or not. In some cases, especially where physicians self-refer their patients for expensive diagnostic tests and treatments, there can be substantial financial incentives for ordering interventions that might not be medically necessary.

Several recent studies have explored whether financial incentives influence how physicians practice, and the answer, unsurprisingly, is that they do. In October, for example, a report in the New England Journal of Medicine examined the “self-referral effect” among urologists treating patients for prostate cancer. The study found that doctors are substantially more likely to order radiation therapy for their prostate cancer patients if those doctors have ownership interests in the radiation services they are offering. Over the five-year period from 2005 to 2010, the use of radiation therapy by self-referring urologists in private practice jumped 19.2 percentage points, whereas the rate among their non self-referring peers barely budged, going up just 1.3 percentage points.

Jean Mitchell, a professor of public policy at Georgetown University and the author of the report, acknowledges that her study can’t ultimately speak to the motivations of the physicians involved. But she sees reason to be concerned. “There’s been this dramatic trend [among self-referring physicians] toward aggressive treatment of prostate cancer, even though basically the clinical data suggest that we should move away from that,” she says. “The issue is that it seems like [patients are] being steered toward the treatment that is going to have the most financial benefit for the urologist.”

The self-referral effect isn’t unique to radiology. Earlier this summer, a report of the United States Government Accountability Office examined rates of referrals for biopsies and found that between 2004 and 2010, referrals for biopsies more than doubled among self-referring physicians, even while they increased only 38 percent among those who referred outside their own practices. Another report published in Radiology in September found the same pattern among physicians referring for advanced knee imaging.

Of course, self-referrals aren’t all bad: proponents argue that they allow physicians to make diagnoses quickly and that they offer patients easier access to needed tests and treatments. Still, it’s hard for Mitchell not to think physicians are self-referring more than necessary. “I don’t entirely blame the doctors,” she says. “A lot of this is the equipment manufacturers too. They’re out there trying to sell what they manufacture. [But] it’s really scary.”

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As physicians, researchers, and policy experts have grown to recognize the problem of excessive care, there have been a number of attempts to combat the problem. One of the most talked-about provisions of Obama’s Affordable Care Act, for example, is the provision for Accountable Care Organizations (ACOs). Under this provision, a network of doctors and hospitals that agrees to act as an ACO receives financial incentives to figure out how to maximize quality while simultaneously reducing costs and eliminating waste in the system. The idea is to encourage healthcare networks to take more collective responsibility for population health and reward better care, rather than simply more care.

Physician groups are also stepping up to solve the problem. One widely publicized effort is the Choosing Wisely campaign, an initiative of the American Board of Internal Medicine Foundation. Realizing that stewardship of finite resources has been a weakness of the medical community, the campaign set out to promote conversations between doctors and patients about utilizing the most effective tests and treatments while avoiding unnecessary care. To this end, organizers began calling on physician societies to compile lists of the top five tests and procedures in their respective specialties that were most susceptible to overuse. To date, more than 50 physician societies have joined the campaign, each contributing their own “top 5” list.

For Sirovich, these initiatives offer signs of hope. Fifteen years ago, she says, conversations about the harms of medical care or excessive spending weren’t likely to come up, but today, she hears more patients—and fellow physicians—talking about the harms of overuse. “We’re definitely seeing some signs that people are starting to think differently about this,” she says.

But despite hints of change, the problem of overutilization is likely to persist for some time. After all, it took more than a century to construct the current healthcare system, and change does not come easily. “There’s an inertia in how we think about things, there’s an inertia in how we’ve organized our system, and there’s an inertia in parties that benefit from the way things have been,” says Sirovich. “I do think we’re going to be struggling with this for a while.”