Even as medical marijuana becomes more widespread, there's little science to show it works

More and more Americans are turning to marijuana to treat a range of conditions, hoping to shrink cancerous tumors, halt epileptic seizures or manage chronic pain.

But even though half the states and the District of Columbia have broadly legalized marijuana as medicine — many by popular vote — there is little evidence it does any good and scant analysis of the risks, particularly as a cancer drug.

"You have this kind of Wild West phenomenon that's driven by emotion and, truly, largely driven by the marijuana legalization lobby," said Dr. Eric Voth, who has advised the White House as chairman of the Institute on Global Drug Policy, a think tank. "Wait a minute, why don't we do this the right way and figure out what works?"

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For decades, the federal government has used the lack of evidence about marijuana's efficacy to oppose the use of the plant or its components as pharmaceuticals. But many researchers say that very position makes serious examination of marijuana's potential benefits or harm extremely difficult.

So anecdotes of its miraculous potential prevail, with little science to back them up.

"There are tantalizing possibilities but no easy way right now to explore them," said Dr. J. Michael Bostwick, a professor of psychiatry in the Mayo Clinic College of Medicine who wrote a review of medical marijuana's history, politics and research.

The federal government classifies marijuana alongside dangerous street drugs such as heroin and ecstasy. Researchers studying marijuana have to secure funding, get their study approved by the Food and Drug Administration, register with the Drug Enforcement Administration and get research-grade marijuana from the National Institute on Drug Abuse.

Not many have succeeded, though the agencies say they support legitimate research. Groups ranging from the American Medical Association to the Brookings Institution have pushed to make research easier.

It wasn't always this way.

The cannabis plant was used as medicine in the United States for nearly a century. In the 1930s, tabloids and the film Reefer Madness portrayed the drug as an insanity-inducing threat to Americans, and the government began to steeply tax its use.

Congress passed the Controlled Substances Act in 1970, categorizing drugs based on potential for medical use and abuse. A 1972 commission convened by President Richard Nixon recommended that marijuana not be banned, calling it as safe as alcohol. But by then it had been put into the Schedule I category, the most restrictive, "with no currently accepted medical use and a high potential for abuse."

The DEA reaffirmed that position earlier this month in denying two petitions to change marijuana's classification. But the agencies involved in its regulation agreed to steps that on paper should make its study less onerous. While a lab at the University of Mississippi has long been the only place scientists could get marijuana to study, the DEA vowed to allow more researchers to grow the plant, granting broader access.

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Many barriers to research remain, and some researchers fear that change will be slow at best. Yet government agencies have acknowledged the shifting public winds.

"If the scientific understanding about marijuana changes — and it could change — then the decision could change," DEA acting administrator Chuck Rosenberg wrote about marijuana's scheduling. "But we will remain tethered to science, as we must, and as the statute demands."

Contact Claire McNeill at cmcneill@tampabay.com or (727) 893-8321. Follow @clairemcneill.