Improving the comparability of general population surveys on drug use in the European Union. Final report

ENGLISH :
This report presents the results of a European project to improve the comparability of general population surveys on drug use prevalence. The project was commissioned by the EMCDDA and carried out by O+S Amsterdam, in close cooperation with a team of key experts from European Union member states. The findings have been elaborated here into a prototype manual for conducting national-level drug use prevalence surveys. For the short term, the manual is designed to promote the harmonisation of survey practices in EU countries, in order to facilitate comparison of national findings. In the longer term, after trial implementations in national surveys and the completion of some methodological substudies ordered by the EMCDDA, the manual could ultimately result in a European standard for general population surveys on drug use prevalence. Such endeavours are necessary because national surveys still use a plethora of different instruments, reporting formats and methodologies, and that makes comparisons between countries difficult and misleading. Even when identical instruments are used, comparability can still be problematic due to differences in sampling frames, sampling methods, modes of interviewing or research context.
The results presented here are wider in scope than was initially envisaged. The original focus of the project was on the harmonisation of questionnaires (core items and questions) and the standardisation of reporting formats. However, it soon proved necessary to address related methodological issues as well. Broadening the scope of the project has also made it clear that many matters need additional investigation, testing and validation. All the findings reported here are the result of a collaborative and iterative process of decision-making among the members of the expert team. Obviously some compromises were necessary due to divergent national interests.
In accordance with the principal task of the project, this report presents a model questionnaire designed to be applicable throughout Europe. In addition, it proposes guidelines for the design and implementation of general population surveys on drug use prevalence and for the analysis and presentation of the findings.