Comparison of methods and resulting drug use prevalence estimates of health surveys versus drug surveys methods

General population surveys, or school population surveys, represent some of the basic tools of data collection on drug use in the countries of the European Union. Occasionally, the inconsistent findings of surveys in individual states indicate general difficulties with ensuring the representativeness and comparability of the collected data. Hence, apart from collecting and analysing data from 28 European countries, the EMCDDA is also involved in discussions with individual members of the Reitox network about the possible standardisation of data collection and methodological support in the form of research guidelines.

In order to ensure the comparability of data, not only among individual countries but also in time spans within the national borders, surveys on drug use in the general population and the school population should comply with a certain methodological minimum and continuity in the research design. In practical terms it is complicated to fulfil these two requirements as European countries and individual national institutions dealing with drug research can differ in research traditions, primary thematic approaches and available (financial or instrumental) sources.

Efforts at harmonising data collection within a key indicator at European level can interfere with national time spans and hence jeopardise the interpretation of trends. On the contrary, a strict insistence on continuity defies meaningful international comparison. Small differences in the research design can actually influence the validity and comparability of findings: methods used for the selection of respondents, the contexts and techniques of data collection, the structure and contents of questionnaires as well as the way questions are worded, all play a role.

A topic that has been discussed most frequently in the last few years in this connection involves the survey context: that is, differences in methods and findings of studies devoted exclusively to drug use (drug surveys) and studies exploring health and healthy lifestyles in which drug use is only one of many topics (health surveys).

This report summarises the insights gained from a literature review, a review of available data and information collected in a survey of individual national experts on GPS key indicators within the Reitox network. The survey aimed to explore specialist stances on the issue of varying survey contexts and also to find a possible internationally valid scientific agreement that would temporarily replace a costly scientific exploration.