title: Can we predict retention in longitudinal studies of substance use? Findings from the Australian Treatment Outcome Study.
abstract: BACKGROUND
  Longitudinal studies are often threatened by difficulties with sample attrition, high rates of which threaten the validity of study findings. The present study examined methodological and participant characteristics associated with sample retention in the Australian Treatment Outcome Study (ATOS) across 3years.
  
  
  METHODS
  Follow-up interviews were conducted at 3-, 12-, 24-, and 36-months post baseline, with follow-up rates of 89%, 81%, 76% and 70%, respectively. Structured interviews measuring past-month drug use, mental health, criminal involvement and demographic characteristics were administered to participants at baseline and each follow-up. Data were analysed using multinomial logistic regression and generalised estimating equations to produce odds ratios with 95% confidence intervals.
  
  
  RESULTS
  Completing all follow-up interviews was associated with being in treatment (OR 3.62), using other opiates at baseline (OR 3.45), more years of schooling (OR 1.20), and having completed the previous interview (OR 35.04). A history of incarceration was independently associated with not completing follow-up interviews (OR 0.47).
  
  
  CONCLUSIONS
  Retention can largely be predicted at study entry, and is unaffected by changes that occur in the interim. These findings highlight the importance of obtaining and maintaining comprehensive locator information, maintaining strong relationships with treatment agencies, as well as the necessity of patience, perseverance and flexibility.
authors.affiliation: National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia; NHMRC Centre of Research Centre in Mental Health and Substance Use, Australia. Electronic address: c.marel@unsw.edu.au.
authors.forename: Christina
authors.initials: C
authors.lastname: Marel
authors.affiliation: National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia; NHMRC Centre of Research Centre in Mental Health and Substance Use, Australia.
authors.forename: Katherine
authors.initials: K
authors.lastname: Mills
authors.affiliation: National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia.
authors.forename: Shane
authors.initials: S
authors.lastname: Darke
authors.affiliation: National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia; NHMRC Centre of Research Centre in Mental Health and Substance Use, Australia.
authors.forename: Joanne
authors.initials: J
authors.lastname: Ross
authors.affiliation: National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia.
authors.forename: Lucy
authors.initials: L
authors.lastname: Burns
authors.affiliation: National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia; NHMRC Centre of Research Centre in Mental Health and Substance Use, Australia.
authors.forename: Maree
authors.initials: M
authors.lastname: Teesson
mesh_terms: D000293:Adolescent; D000328:Adult; D001315:Australia; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006556:Heroin Dependence / Q000628:therapy*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data*; D016896:Treatment Outcome; D055815:Young Adult
keywords: ATOS; Attrition; Follow-up difficulty; Heroin dependence; Longitudinal cohort study; Retention; Substance use; Treatment outcome