title: How to find future ecstasy-users: targeted and snowball sampling in an ethically sensitive context.
abstract: This article documents the design and the sampling procedures of a prospective longitudinal multidisciplinary study on the neurotoxicity of ecstasy (MDMA): the Netherlands XTC Toxicity Study (NeXT). Targeted and snowball sampling was used to recruit 188 respondents who were ecstasy-naive at baseline. All respondents completed baseline questionnaires and underwent medical and neuropsychological examinations. At the end of a 11- to 26- month follow-up period in which they completed four additional questionnaires, 160 respondents remained (85.1%). A total of 65 participants (40.6%) took ecstasy for the first time during the follow-up period. This paper discusses the ethical dilemmas inherent in a study of this type and the specific problems and solutions that emerged in the sampling. The sampling was tightly constrained by our need to locate respondents who were potential future ecstasy users while also meeting strict medical and technical criteria. The 'intention to use' criterion proved to be a clear-cut inclusion rule that was practical to apply in the fieldwork.
authors.affiliation: Bonger Institute for Criminology, University of Amsterdam, P.O. Box 1030, 1000 BA Amsterdam, The Netherlands. H.K.E.Vervaeke@uva.nl
authors.forename: Hylke K E
authors.initials: HK
authors.lastname: Vervaeke
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Korf
authors.forename: Annemieke
authors.initials: A
authors.lastname: Benschop
authors.forename: Wim
authors.initials: W
authors.lastname: van den Brink
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D005544:Forecasting; D006801:Humans; D033183:Interdisciplinary Communication; D008297:Male; D008403:Mass Screening; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D011446:Prospective Studies; D011584:Psychology / Q000941:ethics; D012931:Social Environment; D019966:Substance-Related Disorders / Q000453:epidemiology*
chemical_list: D018817:N-Methyl-3,4-methylenedioxyamphetamine