The problem with recent medicinal marijuana legislation is that it's not based on actual research. States are deciding certain diseases can be treated with pot, but because the federal government has classified marijuana as an illegal and dangerous drug, research on its health benefits are sparse. It's a catch-22 manufactured by the Drug Enforcement Agency: marijuana is illegal because the DEA says it has no proven medical value, but researchers have to get approval from the DEA to research marijuana's medical value.

As Catherine Saint Louis at The New York Times explains, research has shown that marijuana can alleviate pain and nausea symptoms in people with cancer, H.I.V./AIDS and multiple sclerosis. But medical marijuana laws in several states, including the heavily regulated bill just passed in New York State, also allow marijuana to be prescribed for Parkinson’s disease, Lou Gehrig’s disease and epilepsy, despite there being no high-quality studies supporting the health benefits. In some states the lists go on and on, in an attempt to be inclusive without allowing pot for "headaches" and "pain." 

“I just don’t think the evidence is there for these long lists,” Dr. Molly Cooke, a professor of medicine at the University of California, San Francisco, told The Times. “It’s been so hard to study marijuana. Policy makers are responding to thin data.”

For that, we can thank the DEA. The DEA classifies marijuana as a Schedule I drug, the same rating given to heroin, ecstasy, peyote and LSD. Schedule I drugs have "no currently accepted medical use" and aren't eligible for federal research funding. The DEA's war on medical marijuana has been unrelenting — in 2011, the DEA began cracking down on medical marijuana dispensaries in states where they're legal, even after President Obama said he would leave them alone. That same year DEA Administrator Michele Leonhart rejected a bid to reclassify marijuana, arguing that the "risks of marijuana use have not been shown to be outweighed by specific benefits in well-controlled clinical trials." 

Three years later the DEA hasn't changed its mind. The Multidisciplinary Association for Psychedelic Studies and the Drug Policy Alliance released a report this month condemning the agency's refusal to reclassify marijuana as a Schedule II drug, which would allow the Food and Drug Administration to regulate it as a prescription medicine.

But Congress is pushing for lenience. Earlier this month a bipartisan group of lawmakers wrote to the Department of Health and Human Services requesting increased access to marijuana research. "We write to express our support for increasing scientific research on the therapeutic risks and benefits of marijuana," the letter read, adding:

We need the Administration to stop targeting marijuana above and beyond other drugs when it comes to research. By increasing access for scientists who are conducting studies, we end the Catch-22 of opponents claiming they can't support medical marijuana because there's not enough research, but blocking research because they don't support medical marijuana.

The letter may have helped — the FDA announced this week that it would look at the scientific research on marijuana's medical benefits, meaning it might reclassify the drug.