Science Cannabis

The initial enthusiasm for cannabis in the 1960s and early 1970swas rapidly followed by a wave of reaction in the Western world.Although scientists are supposed to try to minimize bias this hasbeen difficult to avoid in a field so colored by issues of morality andpublic policy. Scientists are human beings; they may consciously orunconsciously design and manipulate research for fame and fortune(grants), and some have been guided by a moral commitment to provingthat cannabis is harmful. Extravagant warnings were given, suggestingthat cannabis was a highly dangerous drug that could cause chromosomaldamage, impotence, sterility, respiratory damage, depressed immunesystem response, personality changes, and permanent brain damage.Most of these claims were later proved to be spurious and thebalanced reviews by Hollister (1986, 1998) and by L. Zimmer & J. P.Morgan (1997) in their entertaining book Marijuana Myths, MarijuanaFacts show how effectively many of them have been demolished. It isthus not necessary to deal with all of these arguments in detail here, butsimply to highlight some of the factors that may determine whether cannabisis considered sufficiently safe to be reintroduced into Western medicineand ultimately whether its overall prohibition remains justified.ToxicityTetrahydrocannabinol is a very safe drug. Laboratory animals (rats, mice,dogs, monkeys) can tolerate doses of up to 1000 mg/kg (milligrams perkilogram). This would be equivalent to a 70 kg person swallowing 70grams of the drug —about 5,000 times more than is required to producea high. Despite the widespread illicit use of cannabis there are very few ifany instances of people dying from an overdose. In Britain, official governmentstatistics listed five deaths from cannabis in the period 1993-1995 but on closer examination these proved to have been deaths due toinhalation of vomit that could not be directly attributed to cannabis(House of Lords Report, 1998). By comparison with other commonlyused recreational drugs these statistics are impressive. In Britain there aremore than 100,000 alcohol-related deaths and at least as many tobacco-