Science Cannabis

is Cannabis Safe? 189CB1 receptor in the brain might prove useful as a treatment for schizophrenia.Clinical trials of the CB1 receptor antagonist SR141716A inschizophrenia are said to be under way.Another curious phenomenon experienced by some cannabis usersis termed a flashback. This is a state of altered consciousness resemblinga cannabis high that occurs during periods of sobriety after the usualeffects of the drug have worn off. The experience can be pleasurable, butmore often it is very unpleasant. This can be disconcerting or even dangerousif the person is driving a car or undertaking some other demandingtask at the time. The mechanisms involved are not understood, althoughit is possible that this is merely a bizarre form of deja vu, orperhaps a sudden acceleration of THC clearance from fat stores could beresponsible.A number of studies during the 1970s and 1980s continued to addressthe question of a causative link between cannabis and long-termpsychiatric illness. The strongest evidence seemed to come from a studyin Sweden by Andreasson et al. (1987). The study involved taking detailedmedical records, information about the social background, anddrug-taking habits of 45,570 conscripts to the Swedish army, and thefollowing up of their subsequent medical history over a 15-year period. Atotal of 4293 of the conscripts admitted having taken cannabis at leastonce, but the cannabis users accounted for a disproportionate number ofthe 246 cases of schizophrenic illness diagnosed in the overall group onfollow-up. The relative risk of schizophrenia in those who had used cannabiswas 2.4 times greater than in the nonusers. And in the small numberof heavy users (who had taken the drug on more than 50 occasions)the relative risk of schizophrenia increased to 6.0. The authors concludedthat cannabis was an independent risk factor for schizophrenia. Atfirst sight these findings seem convincing, but the authors' conclusionshave been widely criticized. It is notable that the cannabis-taking groupalso admitted to using a variety of other psychoactive drugs, and thefindings do not prove any cause-and-effect relationship with cannabis. Itmay be simply that both cannabis use and schizophrenia may be relatedto some common predisposing factor such as personality. Indeed somepsychologists and psychiatrists believe that they can identify psychologi-