Cannabis as a medicine became common throughout much of the world by the 19th century. It was used as the primary pain reliever until the invention of aspirin. Modern medical and scientific inquiry began with doctors like O'Shaughnessy and Moreau de Tours, who used it to treat melancholia and migraines, and as a sleeping aid, analgesic and anticonvulsantjammer
By the time the United States banned cannabis in a federal law, the 1937 Marijuana Tax Act, the plant was no longer extremely popular. Skepticism about marijuana arose in response to the bill.The situation was exacerbated by the stereotypes promoted by the media, that the drug was used primarily by Mexican and African immigrants.