Does Medical Marijuana Work? The Experts Are Divided

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The phrase “medical marijuana” has a nice clinical ring to it, but doctors and researchers are divided on the data: some are confident that smoking pot can help a wide range of pains and other symptoms. Others remain skeptical and say patients can get similar relief from a prescription pill that mimics marijuana.

Meanwhile, regardless of what scientists say, 18 states -- including New Jersey – have decided to let patients legally puff the narcotic smoke. 

Each of those states has its own list of conditions for which patients are eligible for “medicinal cannabis.” California, for instance, has a dozen syndromes on the list, many of them very broad – including cancer, arthritis and chronic pain. New Jersey, coincidentally, has the exact same number of bullet points, but most of them are narrowly defined – including terminal cancer, multiple sclerosis and muscular dystrophy – and there are no large catch-all categories.

To Dr. Margaret Haney, from Columbia University’s Substance Use Research Center, these disparate state lists are evidence that there’s a lack of evidence, when it comes to widely using marijuana for palliative care.

“There are some things we know it works well on, like relieving certain kinds of pain or increasing appetite,” Haney said, citing cancer and HIV treatment as areas that clearly benefit from either smoking marijuana or taking a prescription pill called Marinol, that uses a synthetic version of THC, a key compound found in cannabis. “But the data is much weaker for many of the other indications.”

Others are more upbeat.

A recent meta-analysis in the peer-reviewed journal reviewed Clinical Journal of Pain looked at published research on the efficacy of treating different types of pain, and found that in 27 out of 38 randomized controlled trials, “cannabinoids had empirically demonstrable and statistically significant pain-relieving effect.” (“Cannabinoids” encompasses both herbal, smoked marijuana and other cannabis-related derivatives and synthetics.)

“It could be chronic pain secondary to cancer, chronic pain in multiple sclerosis, arthritic pain, especially rheumatoid arthritic pain, or if you have an injury to a nerve through trauma,” said study author Dr. Sunil Aggarwal, a medical resident at NYU studying physical medicine and rehabilitation, who has a doctorate in medical geography and an upcoming clinical fellowship at the National Institutes for Health.

Aggarwal’s article is intended to be “A Concise Clinical Primer,” as his subtitle puts it, for doctors. Aggarwal is untroubled by the disparate state lists of eligible medical conditions and the mixed evidence for pain relief potency. His reading of the research is that marijuana provides sufficiently potent pain relief with few enough side effects that doctors should be allowed to work with patients and develop their own protocols. He likens these prescriptions to the gray area that surrounds off-label use of FDA-approved pharmaceuticals.

“Many different drugs are approved for one indication but more often are used for something else,” he said. “In the hospital here, we have patients that we treat for pain using Gabapentin. It’s really a seizure medicine, but hardly anyone uses it for anti-seizure medicine, even though that’s what the label says.”

The FDA, of course, doesn’t classify marijuana as a pharmaceutical. It’s technically a Schedule I controlled substance – in other words, an illegal narcotic. But the FDA and the federal government essentially look the other way at the state programs.

One substance the FDA does approve is Marinol, the “synthetic pot,” based on THC and manufactured by a Belgian drug company (but also available generically as Dronabinol).

Pro-cannabis advocates believe Marinol isn’t as effective as smoked marijuana, because the pill only contains THC and doesn’t replicate the other more subtle substances in the plant. Dr. Aggarwal and others say it’s like taking vitamins – there’s some benefit from the pills, but they’re no substitute for getting nutrients via real food. (Marinol's manufacturers, for their part, currently market the drug almost exclusively to increase appetite for people suffering severe nausea as a side effect from cancer and HIV medications.)

Haney and her colleague, Dr. Ziva Cooper, have rigorously compared the pain-relieving effects of Marinol and herbal marijuana in a Columbia University laboratory in Washington Heights, overlooking the Hudson River. They give experiment volunteers real and placebo marijuana cigarettes and Marinol pills and then subject them to various stimuli, including cognitive tests on a computer and mild pain, from immersing their hands in ice-cold 39-degree water.

In a recent study in the Neuropsychopharmacology, an imprint of the prestigious journal Nature, Cooper found that “change in pain sensitivity and tolerance did not differ between marijuana and dronabinol.”

“Oral THC was slower to peak, but it was more sustained than smoked marijuana,” Cooper said, in an interview. “[With smoked marijuana] we saw a much faster peak to that pain relieving effect, but we also a fast decrease back to baseline.”

Drs. Cooper and Haney are among a very small group of researchers licensed by federal authorities to use herbal marijuana in laboratory studies.

I asked them what they made of both the research and the anecdotes suggesting smoked marijuana provides pain relief for a wide range of symptoms that other substances, including Marinol, don’t help. They said they understand why people might feel better while smoking marijuana than taking other painkillers. But they said there is often a strong placebo effect among patients hoping and expecting drugs to work, and many pro-marijuana researchers don’t take those forces into account.

Haney said relatively few other studies use placebo controls as rigorously as she and Cooper do – so the other researchers’ data is much less reliable.

“You can’t just give someone a pill and say, ‘What does that do?’ and give them a joint, and say, ‘What does that do?’” Haney said, “because guess what’s going to win? The joints are gonna win every single time.”

Hundreds of doctors have registered to prescribe medical marijuana in New Jersey – and many thousand have in the other 17 states that allow it. The federal Food and Drug Administration, which typically exercises an iron grip over prescription drugs, has basically agreed to look the other way.

In New York, medical marijuana bills have passed in the state Assembly before. Staten Island State Senator Diane Savino believes a bill could get through her chamber, this year, too. Gov. Andrew Cuomo has said he’s mostly opposed to it, but “has an open mind” and would take a closer look, now that the annual budget has passed.