THE CAUSE OF THE AUSTRALIAN HEROIN SHORTAGE: TIME TO RECONSIDER?

We thank Drs Caulkins, Reuter and Smithson for their comments regarding our simple study, which was largely initiated to respond to the claim that ‘no similar shortage occurred at the same time in other markets whose heroin originated in the same countries as Australia’s’[1]. Our findings undermine an argument central to the conclusion that the Australian heroin shortage was caused by local factors, such as law enforcement activities [2], by demonstrating that similar changes occurred in a heroin market in another country also supplied by Burma. In considering the literature to date on the causes of the Australian heroin shortage, concerns remain regarding the standard of proof used in arriving at the conclusion that the shortage was caused by local law enforcement. As Caulkins and Reuter (2006) rightly point out, ‘there are few instances in which drug law enforcement can claim more than transitory success’[3], and the pattern of increased law enforcement activity followed by a sustained reduction in heroin availability is so extraordinary that policy-makers would be wise to question whether this pattern is explained by other factors. For instance, with regard to limitations of current supply control efforts, consider that within Australian and Canadian prisons, some of the most tightly controlled environments on Earth, illicit opiate markets have persisted despite the application of extreme supply reduction efforts that could never be replicated at the community (let alone national) level [4,5]. With respect to the specific comments regarding our article, we agree that the decline in the various indicators for the Vancouver heroin shortage may not coincide exactly with the Australian shortage, which became most evident in late 2000. However, given how geographically distinct the Canadian and Australian heroin markets are, we believe it is overly simple to suggest that changes should be expected to occur at exactly the same time if the shortages are to have a common cause. In this context, we believe that the sharp and sustained decline in daily heroin use among Vancouver injection drug users beginning in the last quarter of 2000 is actually quite thought-provoking, and we provide these data stratified by quarter for the years 1997–2004 (Fig. 1). While Caulkins & Reuter point out that some indicators from our study, such as naloxone use, appear to have begun to decline as early as 1999, this is consistent with their assertion that ‘purity in Melbourne fell gradually but steadily from 70 to 75% in early 1999 to ∼40% in late 2000.’ Similarly, it should be noted that various indicators of heroin-related harm declined at different times in Australia [1]. Daily heroin use among Vancouver injection drug users. Source: all participants followed during the relevant quarter in the Vancouver Injection Drug Users Study (13 307 visits in total) We agree with our colleagues that the abruptness of the Australian heroin shortage may differentiate it from the less abrupt decline in heroin availability observed in Vancouver [3]. However, very abrupt declines in heroin use are not unique to Australia, and available data from Thailand suggest an impressively abrupt decline in heroin use in that nation that preceded the subsequent declines in Canada and Australia [6]. Regardless, with respect to this issue, we do not understand how the rate of change in heroin supply supports one explanation for a heroin shortage (e.g. law enforcement) over another, or rules out the possibility that the Vancouver and Australian heroin shortages have a common cause. Consider the complexity of heroin markets, and the fact that the Taliban's ban on opium cultivation in Afghanistan in 2000 resulted in a 94% reduction in opium production, and yet Afghanistan's major market for heroin in Western Europe has not shown an abrupt heroin shortage [7]. As has been well articulated by Smithson (2005), even studies showing temporal correlations between the reduction in heroin supply in Australia and local enforcement efforts are limited in that they fail to consider a large number of unmeasured potential confounders and hence these associations may reflect simple temporal correlation rather than causation [2]. As an example, given the way that Vancouver's daily heroin use decline appears to so closely coincide with the most abrupt stage of the Australian shortage (Fig. 1), we expect that misleading statistical correlations could be shown between increased local law enforcement efforts in Australia and the downturn in daily heroin use in Vancouver. There is one additional and obvious shortcoming in the current logic used to support the increasingly prevalent belief that local heroin seizures caused the Australian heroin shortage [2]. In 2003–04 Australia recorded the lowest heroin seizure levels in a decade and yet, despite the reduced enforcement activity, the median heroin purity levels remained below 2000 levels [8]. This observation is inconsistent with the explanation that seizures are the causal force behind the ongoing Australian heroin shortage, unless new explanations are developed to fit the evolving trend. It has been suggested by Smithson (2005) that ‘major seizures should act as a deterrent to future attempts at importation’[2], but this explanation would be best supported if heroin supply rose (or at least did not go down) in other markets in the same supply network. An alternate explanation, which is consistent with the declines in heroin use in Thailand that preceded the Australian and Canadian shortages, is that there was an overall gradual shift in production in source countries. This theory is supported by the fact that both Canada and Australia are currently experiencing record-low heroin seizure levels and persistently low street-level supply. The longer the shortages last in Australia and Canada without ongoing seizures to explain these trends, the less likely it would seem they are due to Australian enforcement activities occurring in the late 1990s. We agree with Smithson (2006) that more knowledge regarding the causes of the Australian heroin shortage is needed [9]. However, while the mystery of the Australian heroin shortage continues to unravel, policy-makers should not ignore what is already known about the limits of supply reduction [10]. In light of this wealth of knowledge, and the fact that there has been a reduction in heroin supply in Canada coinciding with the Australian heroin drought, we believe that external global heroin supply forces deserve greater investigation and credence as a potential explanation for the Australian heroin shortage.

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