Therapy Contamination as a Measure of Therapist Treatment Adherence in a Trial of Cognitive Behaviour Therapy versus Befriending for Psychosis

Abstract

High quality randomized controlled trials (RCT) of psychotherapeutic interventions should ensure that the therapy being tested is what is actually delivered. However, contamination of one therapy into the other, a critical component of treatment adherence, is seldom measured in psychotherapy trials of psychosis. The aim of the study was to determine whether a purpose-designed measure, the ACE Treatment Integrity Measure (ATIM) could detect therapy contaminations within a controlled trial of cognitive behavioural therapy (CBT) versus Befriending for first-episode psychosis and to compare the ATIM to a more traditional adherence measure, the Cognitive Therapy Scale (CTS). Therapy sessions were audio-recorded and at least one therapy session from 53 of the 62 participants in the RCT was rated by an independent rater using the CTS and ATIM. Ninety-nine therapy sessions were rated. All Befriending sessions and all but three CBT sessions were correctly identified. The ATIM showed that 29 of the 99 (29%) sessions were contaminated by techniques from the other therapy. Within the CBT sessions, 19 of the 51 sessions (37%) were contaminated by one or more Befriending techniques. Of the Befriending sessions, 10 of 48 (21%) were contaminated by ACE techniques. The mean CTS score was higher in the CBT than the Befriending group. The ATIM was able to detect contaminations and revealed more meaningful, fine-grained analysis of what therapy techniques were being delivered and what contaminations occurred. The study highlights the benefit of employing purpose-designed measures that include contamination when assessing treatment adherence.