Medical marijuana has been gaining support among states and doctors, but one pot researcher points out much remains unknown scientifically about what medical conditions the drug can actually help.

Dr. Margaret Haney is the director of the Marijuana Research Laboratory at Columbia University in New York. Her lab is one of a handful that receives government funding for studies on marijuana, including research on potential therapeutic uses of the drug.

“I have no trouble finding volunteers,” she joked to CBS News' Kera Rennert.

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But these studies are crucial, Haney points out, because carefully controlled studies on marijuana’s effects are lacking. When a new drug gets approved by the Food and Drug Administration, researchers have to demonstrate in series of studies that the drug outperforms a placebo pill to cause a therapeutic effect. This is not the case for marijuana in its plant form.

“The testing is critical, because marijuana is the only medication that’s been voted in as a medication, where we have very established procedures for determining whether something is a medication,” she explained.

Marijuana contains about 60 chemical components called cannabinoids. The most well known and well-studied is delta-9-tetrahydrocannabinol, or THC, which is behind the drug’s "stoned" effect.

Scientists like Haney are starting to isolate those other compounds to see what effects they have. But the lack of research hasn't stopped states from moving forward with legalization.

Medical marijuana is legalized in 20 states in addition to the District of Columbia: Alaska, Arizona, California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Massachusetts, Michigan, Montana, Nevada, New Hampshire, New Jersey, New Mexico, Oregon, Rhode Island, Vermont and Washington. Other states are considering legislation.

The medical community also appears to be increasing acceptance. A survey in the New England Journal of Medicine last March found 76 percent of doctors were in favor of the use of medical marijuana when presented with a hypothetical case of a patient with breast cancer that’s spread and caused pain.

Dr. Sanjay Gupta publicly reversed course and came out in support of medical marijuana, and even apologized for being too dismissive of patients’ reports of symptoms improving.

While medical marijuana is approved in some states for conditions including epilepsy, inflammatory bowel disease multiple sclerosis and chronic pain, the scientific evidence has yet to catch up. Haney notes there is solid evidence marijuana can decrease nausea and increase food intake in people with HIV or cancer who are getting chemotherapy. This has also been shown with the pill form of THC, dronabinol.

One experiment suggests one cannabinoid called cannabidiol, when isolated in high levels, might treat neuropathic pain in mice, a type of chronic pain that can be caused by HIV and chemotherapy.

Research is also being done at other ways to isolate and deliver cannabinoids to patients, since smoking can be a respiratory irritant. Researchers have been testing a marijuana mouth spray Sativex that contains delta 9-THC and cannabidiol. It’s currently approved in some European countries.

Such rigorous trials are necessary, Haney emphasized, to better understand how marijuana might treat medical conditions, if at all. Her tests include having people smoke real marijuana or a placebo so she can disseminate what the drug actually does for appetite, pain or withdrawal from what people think it will do.

But since this research is very much ongoing, she warns people should not believe marijuana is a cure-all as some rent-a-doctors in states with legalization may suggest.

“Just like you’re skeptical of a pharmaceutical industry and what they say a drug does, you have to be just as skeptical about what marijuana does, because people are making enormous profit from it,” said Haney. “That is again why we need carefully controlled studies to demonstrate what it works for and what it doesn’t work for.