the catch-22 of medical marijuana science

NYTimes |  New York moved last week to join 22 states in legalizing medical marijuana for patients with a diverse array of debilitating ailments, encompassing epilepsy and cancer, Crohn’s disease and Parkinson’s. Yet there is no rigorous scientific evidence that marijuana effectively treats the symptoms of many of the illnesses for which states have authorized its use.

Instead, experts say, lawmakers and the authors of public referendums have acted largely on the basis of animal studies and heart-wrenching anecdotes. The results have sometimes confounded doctors and researchers.

The lists of conditions qualifying patients for marijuana treatment vary considerably from state to state. Like most others, New York’s includes cancer, H.I.V./AIDS and multiple sclerosis. Studies have shown that marijuana can relieve nausea, improve appetite and ease painful spasms in those patients.

But New York’s list also includes Parkinson’s disease, Lou Gehrig’s disease and epilepsy, conditions for which there are no high-quality trials indicating marijuana is useful. In Illinois, more than three dozen conditions qualify for treatment with marijuana, including Alzheimer’s disease, lupus, Sjogren’s syndrome, Tourette’s syndrome, Arnold-Chiari malformation and nail-patella syndrome.

“I just don’t think the evidence is there for these long lists,” said Dr. Molly Cooke, a professor of medicine at the University of California, San Francisco, who helped research a position paper on cannabis for the American College of Physicians. “It’s been so hard to study marijuana. Policy makers are responding to thin data.”

Even some advocates of medical marijuana acknowledge that the state laws legalizing it did not result from careful reviews of the medical literature.

“I wish it were that rational,” said Mitch Earleywine, chairman of the executive board of directors for Norml, a national marijuana advocacy group. Dr. Earleywine said state lawmakers more often ask themselves, “What disease does the person in a wheelchair in my office have?”

Research into marijuana’s effects is thin not because of a lack of scientific interest, but chiefly because the federal government has long classified it as a Schedule 1 drug with “no currently accepted medical use.” Scientists who want to conduct studies must register with the Drug Enforcement Administration and win the approval of the National Institute on Drug Abuse, which is the only supplier of legal, research-grade marijuana and can decline to supply it.