Predictors of response to CBT and IPT for depression; the contribution of therapy process.

Little is known about the factors that contribute to a positive psychotherapy outcome. There is still considerable debate as to whether specific factors (e.g. severity of symptoms, comorbidity) or nonspecific factors (e.g. alliance, therapy process) are most important in influencing outcome. This study examined the additional contribution that therapeutic process and alliance made to previously identified specific predictors of response to CBT and IPT for depression over the course of therapy. The previously identified specific factors were belief that childhood reasons caused the depression, recurrent depression, perceptions about how logical therapy was and comorbid personality disorder symptoms. One hundred and sixty five adult outpatients with major depression were treated for depression in a randomised clinical trial examining predictors of response to Cognitive Behavior Therapy and Interpersonal Psychotherapy. All therapy sessions were audiorecorded to enable objective ratings of therapeutic process and alliance. Process factors - patient psychic distress, patient participation and patient alliance had the strongest associations with outcome. The early and middle stage of therapy process did not account for any additional variance other than that previously identified by the patient predictors, however, at the end stage of therapy process contributed a further 14%.