Dan Shapiro was the first person I knew to use medical marijuana. As a junior at Vassar College in 1987, he was being treated for Hodgkin’s lymphoma with potent chemotherapy that caused severe nausea and vomiting. When Dan’s mother learned that smoking marijuana could relieve the distressing side effect, to help her son, this otherwise law-abiding woman planted a garden full of the illegal weed in her Connecticut back yard.

Decades later, marijuana as medicine has become a national phenomenon, widely accepted by the public. Although the chemical-rich plant botanically known as Cannabis sativa remains a federally controlled substance, its therapeutic use is now legal in 36 states and the District of Columbia.

Yet experts in the many specialties in which medical marijuana is said to be helpful have only rarely been able to demonstrate its purported benefits in well-designed scientific studies. And they caution that what is now being legally sold as medicinal marijuana in dispensaries throughout the country is anything but the safe, pure substance Americans commonly expect when they are treated with licensed medications. [Read more at The New York Times]