The efficacy of interpersonal psychotherapy (IPT) to treat depression and other disorders is well established, yet it remains unknown which patients will benefit more from IPT than another treatment. This review summarizes 46years of clinical trial research on patient characteristics that moderate the relative efficacy of IPT vs. different treatments. Across 57 studies from 33 trials comparing IPT to pharmacotherapy, another psychotherapy, or control, there were few consistent indicators of when IPT would be more or less effective than another treatment. However, IPT may be superior to school counseling for adolescents with elevated interpersonal conflict, and to minimal controls for patients with severe depression. Cognitive-behavioral therapy may outpace IPT for patients with avoidant personality disorder symptoms. There was some preliminary evidence that IPT is more beneficial than alternatives for patients in some age groups, African-American patients, and patients in an index episode of depression. The included studies suffered from several limitations and high risk of Type I and II error. Obstacles that may explain the difficulty in identifying consistent moderators, including low statistical power and heterogeneity in samples and treatments, are discussed. Possible remedies include within-subjects designs, manipulation of single treatment ingredients, and strategies for increasing power such as improving measurement.
Keywords: Aptitude-treatment interaction; Interpersonal psychotherapy; Moderator; Personalized medicine.
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