Stress, depression, and the therapeutic alliance as mediators on the outcome of brief psychodynamic-interpersonal psychotherapy for multisomatoform disorder.

The aim of this study was to identify and explore mediators of psychodynamic-interpersonal psychotherapy (PIT) on treatment outcome in multisomatoform disorders (MSD). Data from 164 patients with MSD who took part in a randomized control trial of PIT (= 88) vs. enhanced medical care (EMC; = 76) were re-analyzed. A parallel mediation analysis was performed to investigate whether the beneficial effect of PIT vs. EMC on physical quality of life (physical component summary (PCS) of the SF-36 Health Survey) nine months post-treatment is mediated by post-treatment scores of stress, depression, and therapeutic alliance. The potential mediators were operationalized with the Helping Alliance Questionnaire (HAQ; therapeutic alliance), the Patient Health Questionnaire (PHQ)-stress module (perceived stress) and the PHQ-depression module (PHQ-9; depression). Stress partially mediated the effect of PIT vs. EMC on the follow-up outcome. PIT (as compared to EMC) led to lower post-treatment stress-levels, which in turn led to higher physical quality of life at follow-up. Neither depression nor the alliance had a mediating effect. Stress mediated the outcome of PIT for MSD. Future studies are needed to extend the scope of research regarding which specific psychotherapeutic mechanisms of change are beneficial in PIT treatment of MSD patients.