Marijuana plant © David McNew, Getty Images

Two sets of recent poll results suggest that both doctors and the public have come around on the question of cannabis use. But the resurgent Affordable Care Act, which has exceeded its original target for insurance exchange enrollments, offers no relief to patients who struggle to afford the cost of marijuana prescribed by their physicians. And the drug's status, in the eyes of both the federal government and the insurance industry, appears to be caught in a catch-22 of legality and established effectiveness.

On the question of the drug's safety, Pew reports that, "by wide margins, the public views marijuana as less harmful than alcohol, both to personal health and to society more generally." That margin overall is almost five-to-one, and includes majorities of more than two-to-one in every demographic category. Regarding legality, Pew detects "a major shift in attitudes": "As recently as four years ago, about half (52 percent) said they thought the use of marijuana should not be legal; 41 percent said marijuana use should be legal. Today those numbers are roughly reversed: 54 percent favor marijuana legalization while 42 percent are opposed." Medicinal use of marijuana enjoys broad approval, with majorities saying it should be legal in almost every demographic and partisan group.

Meanwhile, an unscientific survey conducted by WebMD set out to test doctors' attitudes toward the drug and found that a majority say "medical marijuana should be legalized nationally and that it can deliver real benefits to patients." Of 1,544 physicians surveyed, 69 percent said that cannabis "can help with certain treatments and conditions," and 56 percent supported "making it legal nationwide." Support for medicinal marijuana varied by field, but even among the specialists who expressed the lowest level of approval -- rheumatologists -- a majority favored legalization (54 percent). Not surprisingly, since marijuana is often used to treat cancer pain and the side effects of chemotherapy, oncologists and hematologists expressed the highest level of support for the drug (82 percent).

Though medicinal marijuana is legal in 20 states and the District of Columbia, prohibition is still in force at the federal level. Under the Controlled Substances Act of 1970, marijuana is classified as a Schedule I drug, which means that in the government's view it cannot be used safely even under medical supervision. (Cocaine and morphine, by contrast, are Schedule II controlled substances, out of deference to their "currently accepted medical use in treatment.") So according to Uncle Sam, no prescriptions for cannabis can legally be written. Even investigating the drug's medical value is difficult: Research-grade marijuana is controlled by the National Institute on Drug Abuse, which is interested in studying addictiveness, not therapeutic potential.

The government's position is a boon for health insurance companies, which of course don't want to pay for anything they don't have to. Obamacare has compelled insurers to make some changes to their penny-pinching ways: they can no longer deny coverage for people with preexisting conditions (or charge them more), and lifetime or annual dollar limits on essential health benefits are now prohibited. But the ACA doesn't solve the problem of companies declining to cover certain treatments prescribed by physicians.

"Medical marijuana should be covered by health insurance plans like any other doctor-recommended medicine," said Shaleen Title, an attorney and board member of reform advocacy group Marijuana Majority. "But unfortunately for patients, the Affordable Care Act doesn't affect patient use of medical marijuana because health insurance plans currently don't cover it."

There is some relief available from providers, Title explained: "Many dispensaries in legal marijuana states help by offering discounts to patients with financial hardships." But she senses an opportunity for companies to align themselves with the attitudes of doctors and their patients: "Due to rising public support, it might make good sense for a forward-thinking health insurance plan to offer medical marijuana coverage; the first insurance company to do so could attract lots of new customers."

According to Susan Pisano, spokesperson for the trade association America's Health Insurance Plans, the lack of coverage for medicinal marijuana isn't just about the federal government's legal stance -- though she did mention that first when asked why companies won't pay for it. "If you step back," Pisano said, "and you're looking at any service or treatment -- prescription drugs, etc. -- what drives coverage is evidence that something's safe and effective, whatever it is." And with respect to marijuana, "there continues to be concern about a lack of evidence about the benefits, but also concern about the potential harm from inhaling, and a call for research to be able to isolate any beneficial components and make that available in a form that isn't smoke."

Pisano said the health care industry is now more focused than it once was on scientific evaluation of treatments. "There used to be less reliance, frankly, on the evidence," she said. "What, over time, companies are understanding is that that's done two things -- one of which is compromise patient safety, in some instances, and the other is drive up costs."

As an example of this shift, Pisano mentioned the use of autologous bone marrow transplants to treat breast cancer in the 1990s. The procedure was publicized as a life-saving intervention, only to be found both costly and no more effective than alternatives. "It was touted as a treatment that was working for women with late stage breast cancer," Pisano recalled, "so much so that a dozen states and the Federal Employees [Health Benefits] Program actually required that it be covered. And then when the evidence began to come in it was really discredited. It was not even as effective as the standard treatment. It was very debilitating, and made the last months of women's lives very difficult."

Pisano says the same questions remained unanswered about medicinal marijuana: does it work, and is it better than existing therapies? "It gets muddied because of the particular treatment that they're talking about, and the intense public debate about it," she said. "But today's standards demand good evidence."

More from TheStreet