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

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).