Methods and definitions

National routine information on drug use and patterns of use among prisoners is rare. Most of the data available in the EU come from ad hoc studies carried out at local level among samples of prisoners that vary considerably in terms of size. This makes extrapolation within a country very difficult, and the prisons examined are often not representative of the whole prison system. The lack of repeated surveys impedes trend analysis in most of the EU countries.

The data presented here come from a range of sources, which are often not comparable in terms of the methods used. Variations across countries and across surveys make comparisons between and within countries difficult and are related to issues such as: sampling strategy; sample size; geographical coverage; population selection (convicted/remanded, male/female, etc.); measure of drug use (self-report, medical assessment, etc.); drug use and prevalence definitions (lifetime or last year or month prevalence; frequency measures, etc.).