Reanalysis of Efficacy of Interpersonal Psychotherapy for Antepartum Depression Versus Parenting Education Program: Initial Severity of Depression as a Predictor of Treatment Outcome

Objective: Interpersonal psychotherapy (IPT) is supported by substantial empirical evidence as a treatment for depression. Surprisingly, our recently reported randomized, single-blind, controlled clinical trial found no significant difference between interpersonal psychotherapy for antepartum depression (IPT-P) and a parenting education program (PEP) control condition for the treatment of prenatal depression. Because depression severity has been found to influence treatment response in antidepressant treatment trials, the current study reassessed IPT-P outcomes, limiting analyses to women with moderate depressive symptoms.

Method: For this reanalysis, 75 of the 110 study participants who met DSM-IV criteria for major depressive disorder and scored ≥ 16 on the 17-item Hamilton Depression Rating Scale (HDRS-17) from 2005 through 2011 were classified as moderately depressed. Linear mixed models were used to examine the longitudinal treatment response on the HDRS-17, the Edinburgh Postnatal Depression Scale (EPDS), and the Clinical Global Impressions Improvement (CGI-I) and Severity (CGI-S) scales.

Results: Although the longitudinal analysis did not reveal a significant interaction of treatment group and visit (ie, treatment response variation), the IPT-P group had significantly lower HDRS-17 and EPDS depression ratings than the PEP group at week 8 (respectively, P = .008 and P = .046); these scores remained low but lost significance versus those for the PEP group at week 12 due to attrition and smaller sample size. For the CGI ratings, the longitudinal analysis revealed significant interaction of treatment groups and visits for the CGI-I (P = .021) and CGI-S (P = .005) ratings. Post hoc analysis showed significant illness improvement and less illness severity for the IPT-P group as measured by the CGI ratings at weeks 8 (P = .007 and P = .003, respectively) and 12 (P = .003 and P = .012, respectively), whereas the PEP group remained relatively unchanged during the study.

Conclusions: The results of this reanalysis indicate that among women with moderate levels of depression severity, IPT-P is markedly more effective than PEP. The significance of baseline severity level in depression is important in treatment trial outcomes and considerably more important in determining treatment decisions for pregnant depressed women.

Trial Registration: ClinicalTrials.gov identifier: NCT00251043