2.2. Setting, recruitment, and participants
drug abuse
RECRUITMENT
The study setting comprised prisons in Sweden on high-, medium-, and low security levels for either men or women. In Sweden, prisons are run by the governmental authority SPPS, and thus all prisons are state prisons without exceptions. Prisons are specific for women and men, but inmates with a variety of sentences can be placed in the same prison. Normally, with the exception for bad behaviour, inmates are transferred to lower security prisons in a stepwise manner during their sentence, in line with the overall focus on rehabilitation within the SPPS. All inmates have compulsory, scheduled activity in prison for six hours per day during weekdays. Activities include occupational activity, studies on elementary to university level, and rehabilitation programmes. About 26% of inmates participate in rehabilitation programmes. These are manual based, commonly include cognitive behavioural therapy focusing on target behaviours such as criminality, violence, or drug abuse, and can be either in individual or group format [In this study, recruitment of prisons and participants was undertaken as follows. First, all prisons with trained group leaders or a plan to train group leaders during 2019–2020 were invited to participate. Prisons that agreed to participate (n = 15, intervention = 8, control = 7) were allocated to intervention or control condition based on the operation planning as described above (see 