Is marijuana a gateway to opioids?

During a hearing on the 1937 law that effectively banned cannabis throughout the United States, a congressman asked Federal Bureau of Narcotics Commissioner Harry Anslinger “whether the marihuana addict graduates into a heroin, an opium, or cocaine user.” Anslinger, who at that point was blaming marijuana for inspiring outbursts of vicious and irrational violence, said he had seen no evidence that its users progress to other drugs. “I have not heard of a case of that kind,” he said. “I think it is an entirely different class. The marihuana addict does not go in that direction.”

By the early 1950s, Anslinger had changed his mind. “Over 50 percent of those young [heroin] addicts started on marijuana smoking,” he told a congressional committee in 1951. “They started there and graduated to heroin; they took the needle when the thrill of marijuana was gone.”

Anslinger reiterated that point four years later, when he testified in favor of stricter penalties for marijuana offenses. “While we are discussing marijuana,” a senator said, “the real danger there is that the use of marijuana leads many people eventually to the use of heroin.”