In patients with depression, there is no significant difference in the relapse rate after treatment with either interpersonal psychotherapy (IPT) or cognitive therapy (CT), suggesting that either therapy may be useful psychological options for managing depressive symptoms, according to a study published in the American Journal of Psychotherapy.
A total of 182 patients (mean age, 40.5±12.2 years) with depression were enrolled from a single center in the Netherlands. Patients were randomly assigned to receive either CT (n=76) or IPT (n=75) or to a 2-month waitlist control condition followed by the participant’s treatment of choice (n=31). The treatments involved 16 to 20 individual 45-minute sessions, with a mean number of 17±2.9 sessions.
There were 5 study therapists per treatment condition, offering sessions weekly as well as on a flexible basis later in the treatment. Depression severity, the primary outcome, was first measured with the Beck Depression Inventory-II (BDI-II) and then with the retrospective ratings on the semistructured Longitudinal Interval Follow-up Evaluation (LIFE) at up to 17 months’ follow-up.
From baseline to treatment termination, there was an average decrease in the BDI-II score from 29 to 14 (mild depression), respectively (pre- to posttreatment effect size Cohen’s d=1.72). Both IPT and CT were significantly better than the waitlist control for improving depressive symptoms and reducing the likelihood of relapse after treatment termination. Patients receiving IPT or CT also reported significant improvements in quality of life, social functioning, and general psychological functioning (pre- to posttreatment Cohen’s d range, 0.68-1.01).
The researchers found 5 baseline predictors of lower depression symptoms at the end of IPT and CT, including being female, active employment, absence of a personality disorder, low anxiety, and a high quality of life. Baseline values that predicted a differential response in CT and IPT included cognitive problems, somatic complaints, paranoid symptoms, interpersonal self-sacrificing, and an attributional style focused on goal achievement. Of the 6 moderators, cognitive problems predicted better IPT response, whereas the other 5 moderator values at baseline predicted a better CT response.
In terms of the study limitations, the researchers wrote that the study design and analytical methods may not have provided support for sensitive tests of the initial hypotheses or theories about IPT vs CT for managing depression. Nonetheless, they noted that the predictors of treatment success found in this study may promote “the development of treatment selection approaches that can be used to guide clinical decision making in mental health care, thereby advancing the goals of personalized medicine.”
Lemmens LHJM, van Bronswijk SC, Peeters FPML, et al. Interpersonal psychotherapy versus cognitive therapy for depression: how they work, how long, and for whom-key findings from an RCT. Am J Psychother. 2020;73(1):8-14.