Carolien Zeetsen

64 Methods Design A cross–sectional study was performed in which a validated cognitive screening instrument was administered as part of the intake procedure that contains items covering all cognitive domains, the MoCA (Nasreddine et al., 2005). Data were collected between April 2012 and December 2014 in four addiction health care centres. The study was approved by the internal review boards of all participating health care centres and the research board of the Nijmegen Institute for Scientist–Practitioners in Addiction. Participants The aim was to include a total of 800 participants seeking treatment for SUD in one of four addiction health care centres in the Netherlands (IrisZorg, Novadic–Kentron, Tactus and Vincent van Gogh Institute for Psychiatry). The inclusion criteria were 1) dependency or abuse of a substance (excluding nicotine) or behaviour; 2) age 18–75; and 3) signed informed consent for participation. The only exclusion criterion was an inability to administer the MoCA, due to for instance a neurological (e.g. stroke, dementia, traumatic brain injury) or very instable acute psychiatric disorder, severe lack of motivation or insufficient Dutch language skills. Patients were included regardless of substance use status to comply as much as possible with treatment as usual in all participating institutions and to maximize the generalisability of the sample in relation to the population that is referred to addiction clinics in general. Materials Measurements in the Addictions for Triage and Evaluation The Measurements in the Addictions for Triage and Evaluation (MATE 2.1; Schippers et al., 2011) consists of an interview and self–report questionnaires for collecting information relevant for treatment purposes. In this study four sections were used. Section 1 ‘Substance use’, is an interview that assesses the use of nine psychoactive substances and behavioural addictions in the past 30 days as well as lifetime. The primary–problem substance is determined by both the patient and the assessor as the substance that causes the most problems. For the current study, a participant was considered a polysubstance user if any substance other than the primary–problem substance, had a lifetime use of one year or longer, excluding nicotine and behavioural addictions. Section 3 ‘History of treatment for substance use disorders’, assesses if a patient has ever been in treatment for addiction. Section 4 ‘Substance dependence and abuse’, Section Alcohol & Drugs of the Composite International Diagnostic Interview (CIDI; World Health Organization, 1997), is an interview questionnaire that helps to diagnose substance abuse or dependence by answering 11 yes or no questions about the primary–problem substance. Nine out of 11 questions are