title: Self-selection bias in eating disorders outcomes research: Does treatment response of underweight research participants and non-participants differ?
abstract: Observational treatment studies provide a valuable alternative to RCTs but are often criticized due to potential self-selection biases. Studies comparing those who do and do not participate in research on eating disorder treatment are scarce, but necessary to evaluate the impact of self-selection bias on outcomes. All consecutive underweight adult first admissions (N = 392) to an integrated inpatient (IP)-partial hospital (PH) behavioral specialty program were invited to participate in a longitudinal study of eating disorder treatment. Demographic and hospital course data were collected on participants (n = 234) and non-participants (n = 158). Participants and non-participants had similar BMI at admission, lengths of stay, and weight gain rates. Participants were less likely than non-participants to end treatment prematurely from IP and were discharged at a higher BMI; the effect size was small. Few differences in hospital course were observed between participants and non-participants. Although participants were more likely to transition to PH and were discharged at a higher BMI, completion of step-down to PH within this integrated IP-PH program rather than research participation status at admission was a better indicator of discharge BMI, which remains the strongest predictor of long-term weight-maintenance in eating disorders.
authors.affiliation: Johns Hopkins School of Medicine, Baltimore, Maryland.
authors.forename: Colleen C
authors.initials: CC
authors.lastname: Schreyer
authors.affiliation: Johns Hopkins School of Medicine, Baltimore, Maryland.
authors.forename: Graham W
authors.initials: GW
authors.lastname: Redgrave
authors.affiliation: Johns Hopkins School of Public Health, Baltimore, Maryland.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Hansen
authors.affiliation: Johns Hopkins School of Medicine, Baltimore, Maryland.
authors.forename: Angela S
authors.initials: AS
authors.lastname: Guarda
mesh_terms: D000328:Adult; D000856:Anorexia Nervosa / Q000628:therapy*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D017063:Outcome Assessment, Health Care / Q000379:methods*; D015983:Selection Bias
keywords: anorexia nervosa; eating disorders; inpatient treatment; observational studies; research participation; self-selection bias