A TC can be defined as ��a drug-free environment in which people with addictive problems live together in an organized and structured way to promote change toward a drug-free life in the Gemcitabine injection outside society�� [13]. Until the mid-1980s, TCs had a predominant position in most Western addiction treatment systems, but due to the drug and HIV epidemic larger scale harm reduction initiatives (e.g., methadone maintenance, needle exchange programs) became the central focus of most West European drug policies. Despite the long-standing and worldwide availability of TC treatment, TCs were criticized for their limited coverage of drug addicts, the high costs of long-term residential treatment, and the lack of evidence of effectiveness resulting from randomized controlled trials.

Moreover, high drop-out and relapse rates, altered client expectations and social norms and criticism on the impact of lengthy stays in closed communities further questioned the appropriateness of TC treatment around the turn of the century [14].Although outpatient, medically-assisted (substitution) therapy is currently the most common addiction treatment modality [15, 16], one out of three clients in the European Union is engaging in other types of treatment, including therapeutic communities [17]. Recovery-oriented treatment in TCs starts from the widely accepted concept ��community as a method�� [18] and has been implemented on all continents. The standard TC model has been modified to address the needs of specific populations (e.g., women with children, persons with comorbid psychiatric disorders) or new phenomena (e.

g., TCs in prisons, methadone substitution during TC treatment) in the so-called modified TCs (MTC) [19]. The TC method and objectives match well with the emerging recovery movement, since TC treatment can be regarded as an educational process where individuals are supported on their personal journey towards recovery and a drug-free lifestyle and to gain back control over their own lives [20]. Despite a long research tradition in TCs [21, 22], the evidence base for the effectiveness of TCs is limited according to the prevailing Cochrane hierarchy of scientific evidence [23]. Available reviews have been biased by a selective focus on some types of TCs or study designs and a predominant focus on drug abstinence. The frequently cited Cochrane review by Smith and colleagues [23] only included randomized trials, while random group allocation appeared to be either not feasible (i.e., significantly Brefeldin_A higher drop-out among controls) or advisable (i.e., motivation and self-selection are considered to be crucial ingredients of the treatment process) in several studies [24, 25].