As part of its evaluation of Britain’s system for classifying illicit drugs, Parliament commissioned the European branch of RAND Corporation, one of the world’s most respected think-tanks, to study the evidence underlying the classification of several specific drugs, including marijuana. The section on cannabis (marijuana) notes the relatively mild risks of marijuana use and the effective impossibility of a fatal overdose. It also firmly refutes the so-called “gateway theory,” the prohibitionist assertion that marijuana use leads to use of hard drugs like heroin and cocaine: “The gateway theory has little evidence to support it despite copious research.”
Ruth Levitt, Edward Nason and Michael Hallsworth, “The Evidence Base for the Classification of Drugs” RAND Corporation for UK House of Commons, (2006), 86.
Full text available for free at: http://rand.org/pubs/technical_reports/2006/RAND_TR362.pdf