Editor’s note: Today’s entry in the Points Interview series is number twenty-seven, and features Isaac Campos-Costero discussing his recently published Home Grown: Marijuana and the Origins of Mexico’s War on Drugs (University of North Carolina Press, 2012).
Describe your book in terms your mother (or the average mother-in-the-street) could understand.
Between the 1840s and 1920, marijuana was overwhelmingly associated with two effects in 
Mexico– madness and violence. And I really mean overwhelmingly. There were hundreds of reports of marijuana turning its users into violent maniacs and such reports went almost totally unchallenged in published sources. Furthermore, the belief that marijuana caused violent madness appears to have been especially prevalent among the lower classes. In other words, it does not appear that these views were imposed on average Mexicans by propaganda campaigns from above. If you could go back to 1890s Mexico City and ask an ordinary person on the street to describe the effects of marijuana, they almost certainly would have told you that “it makes you crazy.” Of course today marijuana is associated with very different effects. Even the most aggressive drug warriors, in their most hyperbolic moments, would shy away from claiming that marijuana causes violence and madness. That just seems absurd given more recent experience with the drug. Thus my book explains how marijuana earned this reputation. In the process it documents pretty much everything about cannabis’ history in Mexico, from its introduction to the country as a fiber-producing industrial plant in the 1530s, to its nationwide prohibition in 1920. The book thus also traces the origins of prohibitionist drug laws in Mexico and hence the origins of Mexico’s war on drugs. Ultimately I argue that marijuana probably had some role in triggering “mad” behavior and even violence but not because marijuana necessarily causes such effects in any context where it is used, but, rather, because of what researchers have long referred to as “drug, set, and setting”—that is, the interaction between user psychology, the setting of the drug’s use, and the pharmacology of the drug itself. Simply put, what people think is going to occur when they take a drug is often as important as any other factor in producing a particular behavioral effect. Thus if you think a drug should make you lazy, it’s much more likely to make you lazy, and if you think it should make you crazy, it’s much more likely to make you think you are going crazy. Furthermore, marijuana is a substance ideally suited to convince people that “madness” might result from its use. It can produce anxiety, panic attacks, and even hallucinations at high doses (hence its classification as a “psychotomimetic” drug). But, again, like all drugs marijuana’s effects are highly conditioned by the social and cultural setting of its use, and the psychological “set” of its users. In Mexico, a country with the richest collection of hallucinogens on earth and where, since the sixteenth century, disputes over the use of such substances have been intimately linked to political and spiritual conflict, it is not so surprising that the use of marijuana would soon be associated with madness and even violence. And that association has had an enormous historical impact in North America. These ideas not only helped inspire Mexico’s drug-war policies but, as I demonstrate in the book, they also served as the foundation of “reefer madness” ideas in the United States. Thus these Mexican ideas were also crucial to the development of the U.S. war on drugs as we now know it, with marijuana as one of its “big three” targets alongside cocaine and the opiates.