The neglect of treatment-construct validity in psychotherapy research: a systematic review of comparative RCTs of psychotherapy for Borderline Personality Disorder

摘要

BackgroundRandomized 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.