Drug prohibition and enforcement aim to reduce the extent of drug use and the associated harms. The evidence that they succeed is heavily contested. However it is clear that prohibition and enforcement have many consequences other than the intended ones. Many of these negative consequences play a major role in the discussion of drug policy, particularly in face of weak evidence that the principal component of current policy in most countries, namely the enforcement of prohibition, does indeed much reduce drug use. This report is a first effort to provide systematic analysis of the unintended consequences as a group. It distinguishes between those consequences that arise from prohibition per se, such as the lack of quality control, and those that are a function of the intensity and characteristics of enforcement. It identifies seven mechanisms that can generate unintended consequences: behavioral responses of participants (users, dealers and producers), behavioral responses of non-participants, market forces, program characteristics, program management, the inevitable effects of intended consequences and technological adaptation. The report relates this analysis to a recent discussion of the same phenomenon by the Executive Director of UNODC, showing the complementarity of the two approaches for thinking about consequences. This analysis has implications both for policy making and for assessment of policies.

"Prepared for the European Commission"--T.p. "This study has been produced by the Trimbos Institute and RAND with the financial support of the Commission of the European Communities"--T.p.

Introduction -- Definitions -- A taxonomy of mechanisms -- Displacement -- Positive unintended consequences -- Conclusions.