de Zwart & van Laar (Reference de Zwart and van Laar2001) provide a thoughtful discussion of our recent article comparing alternative legal regimes for cannabis (Reference MacCoun and ReuterMacCoun & Reuter, 2001a ). We quite agree that any correlation between a rise in cannabis-selling coffee shops and a rise in cannabis prevalence might be coincidental rather than causal; we said so in our article and highlighted this point in its ‘Limitations’. Our purpose was not to evaluate the Dutch model on its own terms, but to highlight potential risks and benefits of alternative strategies for the USA.
However, we take issue with several points made by de Zwart & van Laar. First, they question the plausibility of our term ‘commercialisation’, noting that since 1991 coffee shops have been subject to criminal prosecution for violations of regulations against advertising. But our article explicitly stated that changes in coffee shop regulation probably reduced commercialisation during the 1990s, and for this reason we explicitly argued that our commercialisation hypothesis was limited to the period 1984-1992. At any rate, this argument confuses formal regulations with their implementation; tourists can attest that cannabis is openly promoted in Amsterdam and other cities, with not-so-veiled references in newspaper advertisements, posters, postcards and shop signs. (Indeed, one can readily verify this by searching for Dutch coffee shop websites on the World Wide Web.)
Second, de Zwart & van Laar claim that “less than half of cannabis consumers purchase the drug in a coffee shop — the majority obtains it elsewhere…”. This statement is apparently based on the Trimbos survey of students. The rule banning minors from coffee shops is difficult to enforce, but one would expect adolescent users to rely less heavily on coffee shops than adult users do. In his intensive longitudinal study of the Amsterdam cannabis market, Jansen (Reference Jansen, Leuw and Marshall1994: p. 172) claims that the shops account for over 95% of cannabis sales in Amsterdam. In their more recent study of 216 experienced cannabis users in Amsterdam, Cohen & Sas (Reference Cohen and Sas1998: p. 63) report that 75% of those still using cannabis reported one or more coffee shops as their primary source of cannabis. Given the accessibility of coffee shops in cities and the fact that one can buy enough for a few days (or weeks) each time, there is hardly more reason to make street purchases of cannabis than of instant coffee. But the 5 g purchase limit surely facilitates secondary transactions in which coffee shop clients share or provide cannabis for their (sometimes younger) friends.
Third, we agree that coffee shops are much more common in Amsterdam than in small Dutch towns, although various estimates in the 1980s suggest that more than half of all coffee shops were located outside Amsterdam. But the concentration of coffee shop sales in Amsterdam actually strengthens our inference that commercialisation might promote cannabis use. Urbanicity has not been shown to be an important correlate of prevalence rates in the USA. Yet the recent national survey by CEDRO (Reference Abraham, Cohen and van TilAbraham et al, 1999) shows that cannabis use was much more prevalent in Amsterdam than in The Netherlands as a whole.
Fourth, de Zwart & van Laar correctly note that school surveys tend to yield higher prevalence estimates than household-based population surveys. Unfortunately, an omitted footnote to our Table 1 obscured the fact that our US source for the “approximately age 18” comparisons was the Monitoring the Future school survey. Trimbos contends that their school survey was specifically designed to facilitate comparisons with that US survey (see Reference Plomp, Kuipers and van OersPlomp et al, 1991: p. 11).
What may be obscured in this exchange is that we hold a mostly enthusiastic view of Dutch drug policy (Reference MacCoun and ReuterMacCoun & Reuter, 2001b ). Indeed, we argue that the coffee shop system has produced few measurable social harms and possibly some benefits by reducing the excessive use of police sanctions and by weakening the link to hard drug markets. Still, an alternative model that might meet the same goals with less risk of promotion is the South Australian system that permits home cultivation of small quantities of cannabis.