for National Geographic News
Earlier this month, the United States Supreme Court ruled that federal drug laws trump policies in ten states that permit medicinal marijuana use.
The decree reignites a smoldering debate among scientists, activists, and lawmakers about how to leverage marijuana's medical benefits while minimizing its potential for abuse.
Known by the scientific name Cannabis sativa, marijuana is an annual herb closely related to the hops used in beer brewing.
Cannabis has been "used since antiquity for both herbal medication and intoxication," according to a 1999 study commissioned by the Institute of Medicine (IOM), a Washington, D.C.-based component of the National Academy of Sciences.
"There is scientific evidence that [marijuana] helps with pain relief and nausea and vomiting from chemotherapy, for example, in terminal cancer patients," said John A. Benson, Jr., a principal investigator of the IOM study and a professor of internal medicine at the University of Nebraska Medical Center.
In addition, some HIV/AIDS patients suffering from decreased appetites use marijuana to "get the munchies," another oft-noted effect of the drug.
Roger Pertwee, a professor of neuropharmacology at the University of Aberdeen's Institute of Medical Sciences in Scotland, noted that "cannabis contains lots of different chemicals called cannabinoids." The most active chemical is delta-9-tetrahydrocannabinol, or THC.
THC binds to specific receptors in the human brain to create the euphoric high associated with smoking pot.
In the early 1990s Pertwee's research group helped to uncover human-produced chemicals similar to THC that stimulate our appetites and help us control pain. "We produce our own cannabis, in effect," he said. "It often seems to have a protective role."
According to Benson, of the University of Nebraska Medical Center, the debate should not be about whether marijuana works to relieve symptoms, but how to best deliver its chemical constituents.
"Smoking is a terrible delivery system," he said. Aside from the potential risk of lung damage, the potency of smoked marijuana is difficult to measure, because THC levels vary widely from plant to plant.
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