Efficacy of interpersonal psychotherapy as a maintenance treatment of recurrent depression. Contributing factors.

In earlier reports, we demonstrated that in patients with recurrent unipolar depression, survival time without a new episode of major depression following discontinuation of medication was significantly and positively related to continued interpersonal psychotherapy (IPT). To determine whether the prophylactic benefit of monthly sessions of IPT was a function of specific features of the intervention, we examined the contribution of the quality of IPT sessions to the length of the well interval in this 3-year maintenance trial. Therapy sessions were rated on specificity and purity of interpersonal interventions. Analysis of these ratings indicated that psychotherapy that was more specifically interpersonal was associated with significantly increased survival time. Patients whose therapy sessions were rated above the median on specificity of IPT had a median survival time of almost 2 years, while those below the median had a median survival time of less than 5 months. We concluded that when patient and therapist are able to maintain a high level of interpersonal focus, monthly sessions of IPT have substantial prophylactic benefit.