Twenty states have so far legalized the medical use of marijuana, and researchers are starting to look at how, exactly, patients can put those laws to the best use.

There’s a burgeoning field of research exploring what medical conditions marijuana is best suited to treat — and how, in certain cases, it might actually outperform traditional medicine. But the evidence remains quite limited, largely as a result of prohibition and strict federal oversight of medical research.

“Millions of patients are using this plant, and we need to understand it,” says Sue Sisley, a doctor and researcher at the University of Arizona. “It is negligent for these 20 states to go selling cards to marijuana patients without actively conducting rigorous medical marijuana research that’s necessary.”

via Six health problems marijuana could treat better than traditional medicine – Vox.