This story was co-published with The New York Times’ The Upshot.

Health insurance companies are no longer allowed to turn away patients because of their pre-existing conditions or charge them more because of those conditions. But some health policy experts say insurers may be doing so in a more subtle way: by forcing people with a variety of illnesses — including Parkinson’s disease, diabetes and epilepsy — to pay more for their drugs.

Insurers have long tried to steer their members away from more expensive brand name drugs, labeling them as "non-preferred" and charging higher co-payments. But according to an editorial published Wednesday in the American Journal of Managed Care, several prominent health plans have taken it a step further, applying that same concept even to generic drugs.

The Affordable Care Act bans insurance companies from discriminating against patients with health problems, but that hasn’t stopped them from seeking new and creative ways to shift costs to consumers. In the process, the plans effectively may be rendering a variety of ailments "non-preferred," according to the editorial.

"It is sometimes argued that patients should have ‘skin in the game’ to motivate them to become more prudent consumers," the editorial says. "One must ask, however, what sort of consumer behavior is encouraged when all generic medicines for particular diseases are ‘non-preferred’ and subject to higher co-pays."

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