"Studies carried out in 15 European countries since 2000 estimated that between 2% and 56% of prisoners have ever used any type of drug while incarcerated, with nine countries reporting levels in the range 20–40% (3). The drug most frequently used by prisoners is cannabis, followed by cocaine and heroin. Estimates of heroin use while in prison ranged from 1% to 21% of prisoners (4). The wide variation in prevalence levels between countries may reflect methodological differences in data collection and reporting. Factors such as price and availability will influence the substances used within prison, but studies suggest a tendency towards the use of depressant-type drugs such as heroin, hypnotics and sedatives or drugs with depressant effects such as cannabis. Stimulant drugs may be less popular, as the effects can be more difficult to manage, for both prisoners and prison staff, within the confined prison setting (Bullock, 2003)."


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, pp. 10-11.