Even doctors inclined to prescribe medical marijuana to patients have been frustrated by a lack of hard data on the drug's effects, the San Francisco Chronicle reported July 9.

Anecdotal evidence suggests that marijuana can help reduce pain and nausea, but there are few controlled studies to back these claims up. Medical-marijuana laws don't allow doctors to prescribe the drug, but they can recommend it to patients. Even after a decade of legal medical use of marijuana in California, however, some doctors are uneasy about the lack of studies.

"You still have a relatively small number of physicians who are in any way active in this," said Steve Heilig of the San Francisco Medical Society. "Reluctance comes from the lack of real information we have and federal attempts to crack down on the use. And there is a real perception that there is a lot of abuse of good intentions, in terms of the pot clubs."

Part of the problem with medical-marijuana research is the difficulty in getting federal grants to study possible medical uses of the drug; getting research published is another challenge. "More and more we're going to find that it (marijuana) has great potential," said Donald Abrams, a medical professor at the University of California at San Francisco. "My fear is, once you get the evidence it's difficult to disseminate it."

Because so few physicians are involved with medical marijuana, patients often rely on the owners of medical-marijuana dispensaries for advice. "A lot of people don't know what they're doing when they walk in," said Kevin Reed, who runs a dispensary. "Doctors don't have enough education. That's what I've seen a huge lack of, is the education. When you're buying from someone like us, you're dealing with people who know those things. We have a regulated environment."