Efficacy and mechanism of change in transdiagnostic CBT for health anxiety and depressive disorders using single case experimental design

Abstract

The main purpose of this study was to evaluate and compare the effectiveness and mechanism of change (MOC) in transdiagnostic cognitive behaviour therapy (tCBT) for health anxiety and depressive disorders using single case experimental design (SCED). The tCBT used in this study was based on Salkovskis’ theory of the change in belief of theory A, an ideographic and unhelpful belief the individual holds pre-treatments, to theory B, a more realistic explanation of the problem. Two participants were recruited, one suffering from health anxiety and one from dysthymia. Measures were taken by self-report questionnaires. Main analysis was visual analysis along with calculations of Reliable change index (RCI) and Wilcoxon signed rank test to evaluate if changes were statistically significant. The tCBT was effective in decreasing health anxiety symptoms and emotional health problems but the participant suffering from dysthymia dropped out of the trial after session one. Believability of the participant with health anxiety in theory A decreased and followed decrease in symptom measures but the belief in theory B did not increase according to Salkovskis’ theory. There was a significant decrease in belief in the Three Most Distressing Thoughts from pre- to post sessions. Visual and statistical analysis suggested that theory A was a probable MOC in the tCBT but that the theory B account was not as striking. Further research is needed.Keywords: Health anxiety, dysthymia, transdiagnostic cognitive behaviour therapy, mechanism of change, single case experimental design.