Evidence for the cognitive mediational model of cognitive behavioural therapy for depression.

BACKGROUND: Although empirical support for the efficacy of cognitive behavioural therapy (CBT) as a treatment for major depressive disorder (MDD) is well established, its mechanism of action is uncertain. In this investigation, we examined evidence for the cognitive mediational model in a randomized control trial involving CBT, interpersonal therapy (IPT) and pharmacotherapy (PHT) in patients with MDD.
METHOD: One hundred and thirty participants diagnosed with MDD were treated with CBT, IPT or PHT. Participants completed the Hamilton Depression Rating Scale, Beck Depression Inventory-II and Dysfunctional Attitudes Scale prior to and following treatment.
RESULTS: The cognitive mediational model, in which dysfunctional attitudes are proposed to mediate depressive symptom reduction in response to treatment, provided a good fit to the data when contrasting CBT v. IPT, with results supporting a mediational role for dysfunctional attitude change in depressive symptom reduction. The complication model, in which dysfunctional attitudes are proposed to be a consequence of depressive symptom reduction, provided a good fit to the data when contrasting CBT v. PHT, with results supporting a mediational role for depressive symptom reduction in dysfunctional attitude change.
CONCLUSIONS: There was no evidence for a mediational role for dysfunctional attitude change in IPT. Changes in dysfunctional attitudes accompanied both CBT and PHT; however, empirical evidence suggests that the role of attitudes in treatment outcome may differ between these two treatments.

RCT Entities:   Population Interventions Outcomes