Non-adherence to the study protocol and non-compliance with the treatment procedures were documented on the various parts of the CRF. Reasons for non-adherence and/or non-compliance included refusal to (further) participate in the study and/or the treatment, death, imprisonment, unacceptable behavior (e.g. violence, smuggling heroin out of the treatment site), and moving to another city. All participants were approached by the research-assistants for all assessments, regardless of whether or not they complied to the study treatment schedule, or still participated in the treatment. Hence, only in exceptional cases - i.e. if a participant could definitely not be reached anymore for assessments - the treating physician filled out the study completion form prior to the end of the planned study period of an individual participant.