California's Proposition 19, the marijuana-legalization measure, went down to defeat in the November election. Earlier in the year, however, scientists in that state conducting the first medical trials on pot and pain in two decades found that yes, marijuana can be effective medicinally. “I think that clearly cannabis has benefits,” said Dr. Donald I. Abrams, a San Francisco oncologist who led that study. “This substance has been a medicine for 2,700 years; it only hasn’t been a medicine for 70."