The Canadian film "The Marijuana Conspiracy," released in the US on 4/20, illustrates in part the absurdity and politicization of research into marijuana's effects. The film, based on a study that happened in 1972 in Toronto, begins with footage of politicians (all old, white men) railing against marijuana use. We then meet an old, white male addiction researcher downing a martini who hires an unscrupulous hippie-type researcher out for fame and fortune who recruits young women pot smokers for a study aimed at discovering marijuana's harms.
The women were locked in a building for 98 days, with no escape to take a walk outside or see their friends or families, while being constantly observed by researchers. Even the joints they were given to smoke nightly couldn't counter the effects of this strange, unnatural setting and the film (and doubtlessly the study itself) devolves into melodrama. Like many rats put in a cage, the women were pointlessly overdosed with pot. Yet, they remained productive and experienced no ill effects, although some members of both the smoking group and the nonsmoking control groups had difficulty assimilating after their isolation. The results of the study were never publicized due to political reasons, and it took decades for Canada to finally legalize pot (the US still hasn't done so).
