Economic models of addiction posit that examination of price elasticity – changes in patterns of use of a drug in conjunction with changes in price – can reveal important clues about the rationale for drug choice. Such studies typically classify pairs of drugs as complements (as price of one drug increases and its use correspondingly decreases, use of other drug decreases) and substitutes (as price of one drug increases, use of other drug increases). While economic studies of cannabis and cigarettes are few, there is growing support for cannabis and cigarettes serving as complements. Pacula (88) used data from the U.S. National Longitudinal Survey of Youth to report that as cigarette prices increased (and cigarette use decreased), marijuana use decreased as well, indicating complementarity. Two additional studies of U.S. data have reinforced this finding (89;90). In a similar study conducted in Australia, Cameron and Williams (91) found that a 10% monetary price increase in cannabis price resulted in a 1.32% drop in past 12 month cigarette smoking. Decriminalization had no impact on cigarette smoking nor did changes in cigarette prices influence past 12 month cannabis use.
