The study assessments were conducted every two months during the course of the individual study period of each participant. The full version of the ASI was administered at the initial screening visit (phase I, day 1; see paragraph 2.3), to obtain detailed information on both the lifetime and recent problem status of the patient. At the subsequent two-monthly assessments, including the baseline assessment (phase II, day 1), either the integral follow-up version of the ASI or the alcohol and drug use section of the ASI was used. Each assessment included the MAP-HSS, SCL-90, and the social supplement of the ASI, in addition to either the integral ASI or the alcohol and drug use section of the ASI, since these instruments and supplements contained the components of the primary outcome measure of the study. In addition, each two-monthly assessment included the physician's medical screening, including - if applicable - registration of co-medication, and (serious) adverse events, which were both documented in the patient's medical file on a continuous basis during the study as well.
Various assessments were conducted at less frequent intervals. These included an extensive medical examination by the treating physician (only at study entry), the CIDI (at study entry and at the end of the 12 months experimental study phase), the client satisfaction questionnaire (at study entry, and after six, 12 and 18 months), and the additional treatment supplement (as the client satisfaction questionnaire, with additional assessments at the initial screening visit, and after 10 and 14 months). Lastly, the pregnancy tests among the female participants, and the urine sampling for drug screening were conducted monthly. From these, the collection of urine samples took place both at the regular two-monthly assessment-visits, and on a randomly selected day in the course of the interval between these two-monthly assessments.