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US marijuana laws clamping the lid on pot research

There are few large-scale studies on medical marijuana users.

Weeded out: The US government arrests medical marijuana users.

A decade after California became the first US state to legalize medical marijuana, one small survey estimates that doctors have recommended the drug to about 350,000 patients. But continuous legal wrangling with the federal government has scared researchers away from tapping into this vast pool to understand how the drug works.

“No one wants to do a bunch of research if medical marijuana is just going to disappear,” says Rosalie Liccardo Pacula, co-director of the Drug Policy Research Center at the nonprofit RAND Corporation. As a result, she says, the past decade has been “a huge uncontrolled public health experiment.”

What makes cannabis so attractive as a medicine is its safety. Philip Denney, Society of Cannabis Clinicians

The California law took effect in November 1996 without an accompanying patient registry or any monitoring scheme. The law grants immunity from state laws to individuals in California who have a recommendation from a physician. But in 2005, the US Supreme Court ruled that those individuals are not protected from federal prosecution.

In October, the federal Drug Enforcement Agency arrested 15 medical marijuana providers and users at eight California cannabis dispensaries, which are legal under the state law.

However, according to the new survey, published in November in O'Shaughnessy's, self-described as “a medical journal/political tabloid,” some California doctors are convinced that marijuana has medical value. The 18 physicians and one network of clinics surveyed had provided recommendations to 140,000 individuals during the past decade, a figure extrapolated to the state. About 95% of them had used marijuana medically before seeking a doctor's approval.

One surveyed specialist, Redding-based Philip Denney who is president of the Society of Cannabis Clinicians, identified the 'typical patient' as a male in his mid-40s with chronic low back pain. Among Denney's 18,900 recommendations for medical marijuana, roughly 50% were for chronic pain, 15% for gastrointestinal disorders, 15% for psychiatric disorders and 10% for neurological disorders such as multiple sclerosis. “What makes cannabis so attractive as a medicine is its safety,” Denney says. “There's no such thing as an overdose.”

In the survey, respondents consistently reported that cannabis helped reduce their reliance on opiates. “A typical story I hear is from the patient who was taking 260 milligrams of oxycontin a day and now with cannabis is down to 10 milligrams,” Denney says.

California in 2002 also funded the Center for Medicinal Cannabis Research, housed at the University of California, San Diego. Among the fourteen clinical trials completed or underway: a placebo-controlled double-blind study of cannabis for neuropathic pain in individuals with HIV/AIDS, a study of cannabis versus the tranquilizer lorazepam for neuropathic pain, and a study of how well cannabis controls spasticity in multiple sclerosis. Researchers funded by the center are also studying how cannabis affects the immune system in those with HIV/AIDS.

“The state of California took a real chance on this,” says Igor Grant, director of the center. “We're on our way to getting some answers.”

Preliminary results in 50 individuals with HIV/AIDS show, for instance, that cannabis reduces neuropathic pain better than a placebo. As results from small trials trickle in, some observers lament the lost opportunity to conduct large-scale studies. Says Robert MacCoun, a law professor who studies drug policy at the University of California-Berkeley, “It's one consequence of this crazy system we have.”

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Vastag, B. US marijuana laws clamping the lid on pot research. Nat Med 12, 1335 (2006). https://doi.org/10.1038/nm1206-1335b

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