title: The neglect of treatment-construct validity in psychotherapy research: a systematic review of comparative RCTs of psychotherapy for Borderline Personality Disorder.
abstract: BACKGROUND
  Randomized controlled trials (RCTs) are considered the best methodology for studying the efficacy of psychotherapy. Optimally an RCT design makes it possible to conclude that if one treatment has a better outcome than another, this is due to the treatment package (TP) as it was implemented in this particular context, rather than other factors beyond the treatment (= high internal validity). Strong internal validity does not, however, provide evidence for the treatment model (TM) that provides the theoretical basis of the TP, because the TP that is tested may differ from the comparison condition in a number of other ways that suggest alternative explanations for the effects. These alternative treatment contrasts represent threats to construct validity of the conclusions. Maximal construct validity requires (1) that the treatments are clearly contrasted on the experimental factors (treatment integrity), and (2) that alternative treatment contrasts can be eliminated. The analysis of alternative explanations is a neglected topic in psychotherapy research. To approach this problem, a methodology for the analysis of treatment contrasts is suggested and tested.
  
  
  METHODS
  Two indexes were defined: (1) a Treatment Integrity Index (TII) and (2) an Alternative Treatment Contrast Index (ATCI). This methodological approach was applied to eight comparative RCTs of treatments for Borderline Personality Disorder (BPD), which were coded for a set of treatment contrasts independently by three coders.
  
  
  RESULTS
  The analysis of the RCTs of treatments for BPD showed that construct validity differed widely between the different studies but was generally low (low TII and ATCI), and that it is therefore difficult to draw causal conclusions from this research. The publication policies of scientific journals in this area seldom require the systematic data relevant to an analysis of alternative explanations of the effects, which is needed to provide evidence for a particular TM.
  
  
  CONCLUSIONS
  Research on psychotherapy needs to be refocused from treatment packages (TP) to treatment models (TM). This requires an improved conceptualization of the methodological principles and skills involved, and the development of valid measures of these, but also improved reporting standards concerning treatment-construct validity in scientific journals.
authors: Department of Psychology, Lund University, Box 213, 221 00, Lund, Sweden. Lars-Gunnar.Lundh@psy.lu.se.
authors: Lars-Gunnar
authors: http://orcid.org/0000-0002-1649-969X
authors: LG
authors: Lundh
authors: Department of Psychology, Lund University, Box 213, 221 00, Lund, Sweden.
authors: Terese
authors: T
authors: Petersson
authors: Department of Psychology, Lund University, Box 213, 221 00, Lund, Sweden.
authors: Martin
authors: M
authors: Wolgast
mesh_terms: D001883:Borderline Personality Disorder / Q000523:psychology / Q000628:therapy*; D006801:Humans; D011613:Psychotherapy / Q000379:methods*; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D013223:Statistics as Topic; D016896:Treatment Outcome
keywords: Alternative explanations; Borderline personality disorder; Construct validity; Internal validity; Psychotherapy; Randomized controlled trials; Treatment contrasts; Treatment integrity; Treatment model; Treatment package