title: The regression discontinuity design showed to be a valid alternative to a randomized controlled trial for estimating treatment effects.
abstract: OBJECTIVE
  To compare treatment effect estimates obtained from a regression discontinuity (RD) design with results from an actual randomized controlled trial (RCT).
  
  
  METHODS
  Data from an RCT (EVIDENT), which studied the effect of an Internet intervention on depressive symptoms measured with the Patient Health Questionnaire (PHQ-9), were used to perform an RD analysis, in which treatment allocation was determined by a cutoff value at baseline (PHQ-9 = 10). A linear regression model was fitted to the data, selecting participants above the cutoff who had received the intervention (n = 317) and control participants below the cutoff (n = 187). Outcome was PHQ-9 sum score 12 weeks after baseline. Robustness of the effect estimate was studied; the estimate was compared with the RCT treatment effect.
  
  
  RESULTS
  The final regression model showed a regression coefficient of -2.29 [95% confidence interval (CI): -3.72 to -.85] compared with a treatment effect found in the RCT of -1.57 (95% CI: -2.07 to -1.07).
  
  
  CONCLUSIONS
  Although the estimates obtained from two designs are not equal, their confidence intervals overlap, suggesting that an RD design can be a valid alternative for RCTs. This finding is particularly important for situations where an RCT may not be feasible or ethical as is often the case in clinical research settings.
authors.affiliation: Department of Psychosomatic Medicine, Center for Internal Medicine and Dermatology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Iris L
authors.initials: IL
authors.lastname: Maas
authors.affiliation: Department of Psychosomatic Medicine, Center for Internal Medicine and Dermatology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany; Population Health Strategic Research Centre, School of Health and Social Development, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia.
authors.forename: Sandra
authors.initials: S
authors.lastname: Nolte
authors.affiliation: Department of Psychosomatic Medicine, Center for Internal Medicine and Dermatology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Otto B
authors.initials: OB
authors.lastname: Walter
authors.affiliation: Department of Clinical Psychology and Psychotherapy, University of Bern, Fabrikstrasse 8, Bern 3012, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Berger
authors.affiliation: Department of Psychology, Clinical Psychology and Psychotherapy, Eberhard Karls University Tübingen, Schleichstrasse 4, Tübingen 72074, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Hautzinger
authors.affiliation: Department of Psychiatry and Psychotherapy, Lübeck University, Ratzeburger Allee 160, Lübeck 23538, Germany.
authors.forename: Fritz
authors.initials: F
authors.lastname: Hohagen
authors.affiliation: Department of Psychology, University of Trier, Trier 54286, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lutz
authors.affiliation: GAIA AG, Gertigstrasse 12-14, Hamburg 22303, Germany; Department of Psychology, City University London, Northampton Square, London EC1V 0HB, UK.
authors.forename: Björn
authors.initials: B
authors.lastname: Meyer
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, Hamburg 20246, Germany.
authors.forename: Johanna
authors.initials: J
authors.lastname: Schröder
authors.affiliation: Department of Psychiatry and Psychotherapy, Lübeck University, Ratzeburger Allee 160, Lübeck 23538, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Späth
authors.affiliation: Department of Psychiatry and Psychotherapy, Lübeck University, Ratzeburger Allee 160, Lübeck 23538, Germany.
authors.forename: Jan Philipp
authors.initials: JP
authors.lastname: Klein
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, Hamburg 20246, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Moritz
authors.affiliation: Department of Psychosomatic Medicine, Center for Internal Medicine and Dermatology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany; Outcomes Measurement Science, Department of Quantitative Health Sciences, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA. Electronic address: matthias.rose@charite.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Rose
mesh_terms: D000328:Adult; D003866:Depressive Disorder / Q000628:therapy*; D015340:Epidemiologic Research Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011613:Psychotherapy / Q000379:methods*; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*; D012044:Regression Analysis; D019114:Remote Consultation / Q000379:methods*; D015203:Reproducibility of Results; D016896:Treatment Outcome
keywords: Causal inference; Depression; Nonrandom group assignment; PHQ-9; Randomized controlled trials; Regression discontinuity design