The epidemiology of drug use at the macro level: Indicators, models and policy-making

Indicators and models may help in studying and understanding the epidemiology of drug use at the international or macro level. Indicators of drug use are usually based on available routine data and give indirect information on prevalence and trends. They can be used to cover large geographical areas with a limited budget; however, they are usually limited in quality and scope. Modelling is based on mathematical theory and can be used to integrate data from different indicators and other sources. It can be used to estimate prevalence and incidence or to enhance the understanding of drug processes by simulating experiments that are difficult or impossible to perform in real life. A sufficient understanding of basic assumptions and limitations is crucial to the interpretation of modelling results. Depending on the availability and use of data, a whole continuum of modelling may exist, ranging from empirical analyses with a high applicability to real life, to theoretical hypothesis-generating exercises based on many assumptions. Compared with other areas, the epidemiology of drug use has so far made little use of modelling, partly because reliable data remain scarce; nevertheless, work on improving indicators and other data is in progress. In the field of drugs, some issues that continue to hamper the application of evidence-based policy-making are lack of a common understanding of priorities for study and intervention, lack of knowledge of the spread and progression of drug problems, and legal and moral discourses. Indicators and models, which are important, complementary tools for epidemiology at the macro level, may help to clarify such issues. Although the quality of data and thus the inferences to be drawn from them are often more limited than they are in in-depth empirical studies, macro-level assessments are necessary to guide national and international policy decisions.