Marijuana is moving from secret stashes in underwear drawers to pharmacy shelves. But what do we know about it?

Humans began cultivating marijuana for medicinal use almost 3,000 years ago. As recently as the middle of the 18th century, it was being used for healing in India. But because it was an illegal drug until recently, research is just getting underway in the West. 

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So far in the U.S., medical marijuana has been approved for use in 23 states and the District of Columbia, while legalization bills are pending in several others, including Pennsylvania. 

“We respond to cannabis because we are built with intrinsic compounds, transmitters and receptors that can be activated by compounds in the cannabis plant,” explains Dr. David Casarett, a University of Pennsylvania professor and author of “Stoned: A Doctor’s Case for Medical Marijuana.” 

He gives us the facts on where the research stands.

Chronic pain: The treatment of chronic pain is one of the most common uses of medical marijuana. But it’s more effective in reducing neuropathic pains, which are caused by injury to the nerves rather than arthritis. “It seems marijuana is more efficient at managing neuropathic pains, which is interesting because they can be very hard to treat using opioids like morphine,” he says.

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PTSD: Marijuana could be an effective way to treat post-traumatic stress disorders. “We don’t have clinical trial data showing how it works, but I think any time you have lots and lots of people using something for one particular reason, we need to figure out why,” the expert says. 

Healing bones: In a recent study, Israeli researchers gave cannabidiol to rats with bone fractures, and found that the healing process was significantly sped up. When tetrahydrocannabinol, which produces the hallucinations associated with pot, was removed, the effects remained.

Insomnia: “We know from medical trials that marijuana can help you fall asleep if you have other symptoms preventing you from falling asleep, like chronic pains,” says Casarett. But more research is needed to prove its effectiveness on patients who don’t have a sleep disorder. 

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Cancer: On the use of marijuana in treating cancer, Casarett is more skeptical. “We know that the cannabinoids in marijuana work well for nausea, including nausea related to chemotherapy,” he highlights, but cautions against believing it has cancer-fighting powers. 

“Some people promote its use, not in the management of cancer-related symptoms, but as an actual treatment, saying that highly concentrated cannabis oil can be used to put cancer into remission,” he recounts. 

“While researching for my book, I talked to a woman who had lymphoma. It was treatable and she had about a 90 percent chance [of survival] if she went through chemotherapy, but she decided to put all of her hopes into this cannabis oil. She died a couple of months ago."