Carolien Zeetsen

113 CHAPTER Cognitive i mpairments in patients with GUD predict relapse 6 Methods Design This study is a prospective, observational, multicentre cohort study, part of a larger monitor of patients with GUD. Due to the observational design, the study was exempted from medical ethical review by the Medical Ethical Committee of the Medical Spectrum Twente. Part of the data of the monitor has already been published as an open label trial with baclofen (Beurmanjer et al., 2018). Participants A consecutive series of patients with GUD (according to DSM–IV criteria of substance dependence, APA, 1994) who were admitted for detoxification at one of six participating addiction health care centres in the Netherlands (i.e. IrisZorg, Mondriaan, Novadic–Kentron, Tactus Verslavingszorg, Victas and Verslavingszorg Noord–Nederland) were recruited ( n = 137). Inclusion criteria were an age of 18–65 years, a need for inpatient GHB detoxification, and comprehension of the Dutch language. One exclusion criterion was the presence of acute psychiatric problems interfering with study participation, such as mania or acute psychosis. A physician screened patients on these criteria before detoxification. All patients signed informed consent, before they were included in the study. Materials Demographic data Demographic data such as sex, date of birth, ethnicity, housing situation, source of income and level of education were collected through self–report. Measurements of the Addictions for Triage and Evaluation The MATE 2.1 (Schippers et al., 2011) is a structured clinical interview that measures the history, frequency and consequences of drug use, including medical, social and psychological problems, and part of it is based on the Composite International Diagnostic Interview (CIDI; WHO, 1997). For this study section 1 ‘Substance Use’ was used to assess GHB and other substance use patterns. During this structured interview patients were asked about their substance use over the past 30 days (number of days and amount used) and lifetime (total years of use of at least three days per week). The MATE 2.1 has a good inter–rater reliability, ranging between 0.75 and 0.92 (Schippers et al., 2010). GHB questionnaire In addition to the questions on GHB use in the MATE 2.1, the GHB questionnaire was included to obtain more detailed information on GHB use patterns (Dijkstra et al., 2017). The original questionnaire has 28 questions regarding motivation for GHB use, first introduction