"Cannabis is the illicit drug with the highest reported level of lifetime prevalence among prisoners, with between 12% and 70% having tried it at some time in their lives. This reflects drug use experience in the general population, although the levels there are lower (1.6% to 33% among 15- to 64-year-olds). Levels of use of cocaine, Europe’s second most commonly reported illicit drug, both inside and outside prison, are also much higher among prisoners (lifetime prevalence of 6–53%) than among the general population (0.3–10%). Experience of amphetamines among prisoners ranges from 1% to 45%, whereas among the general population the range is from almost zero to 12%. Data on lifetime misuse of other substances (such as volatile substances, hypnotics and sedatives) are limited, and prevalence levels, among both prisoners and the general population, are usually low (EMCDDA, 2012).
"Prisoners differ greatly from the general population in their reported experience of heroin. Whereas less than 1% of the general population have ever used heroin, lifetime prevalence levels among European prisoners are much higher, with eight of the 13 countries that were able to provide information on heroin use reporting levels between 15% and 39%."


European Monitoring Centre for Drugs and Drug Addiction, "Prisons and drugs in Europe: the problem and responses" (Luxembourg: Publications Office of the European Union, November 2012), Catalog No. TDSI12002ENC, doi: 10.2810/73390, p. 9.