While the drug therapy is becoming more widely available, the science is still not clear on how it may help.



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Medical marijuana has been approved in 28 states and the District of Columbia, but researchers are still trying to connect the dots as to how, and if, it works.

"Unfortunately, there are almost no uses of medical marijuana that have been subjected to the kind of rigorous testing you'd want for a pharmaceutical," says Dr. Kenneth Mukamal, associate professor of medicine at Harvard-affiliated Beth Israel Deaconess Medical Center. "This does not mean that it has no benefits, but only that the lack of human studies prevents us from being sure if medical marijuana can really help."