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General population surveys of drug use

Drug use in the general population is estimated through representative sample surveys of the whole population. This allows drug use and related factors to be measured directly in the community and at the individual level, providing estimates of the proportion of the population who have used different drugs during certain periods of time. The value of these surveys is clearly increased when samples are large and when they are repeated regularly using the same methods.  The EMCDDA’s Handbook for surveys on drug use among the general population' (1042KB), presents the guidelines for implementing the key indicator 'Extent and patterns of drug use among the general population'. 

For illegal drugs, the standard prevalence measures used are:

  • lifetime experience – any use during a person’s life (lifetime prevalence);
  • recent use – any use during the previous year (last 12 months prevalence); and
  • current use – any use during the previous month (last 30 days prevalence).

Lifetime experience is widely used in reports. It is useful as a framework concept and for filtering further measurements, for understanding social inter-generation dynamics, and it is a prerequisite for estimating drug incidence. Recent use figures give a better description of the immediate situation.  Current use would give more an indication of regular use, especially when focusing on relevant groups (such as males aged 15-24), but prevalence figures – with exception of cannabis – are generally low in the whole population. The combination of lifetime experience and recent use will provide basic insights into drug use patterns such as continuation or discontinuation rates.

Surveys can identify factors that may contribute to differences in overall national figures, for instance, the relative proportions of urban and rural population and inter-generation factors due to the convergence between the lifestyles of young males and females. There are though limitations of surveys in estimating the more marginalised forms of drug use (e.g. heroin injection) due to non-probabilistic errors (exclusion from the sampling frame, absence, non-response).  Moreover, the social context can influence self-reporting of drug use.

There are methodological differences between countries, such as the survey contexts, data collection methods and sampling procedures. An EMCDDA project assessed the impact of different data-collection methods (face-to-face interviews, telephone interviews, postal questionnaires) used in different Member States - the report may be downloaded (415KB).  Comparative analysis across countries should be made with caution, in particular where differences are small, and the formulation of drugs policy and its evaluation should take carefully into consideration age groups, birth cohorts, gender and urbanisation factors among others. 

For more information about the methods used see the detailed notes. 

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Page last updated: Wednesday, 24 November 2004