Moderating Effects of Alexithymia on Associations between the Therapeutic Alliance and the Outcome of Brief Psychodynamic-Interpersonal Psychotherapy for Multisomatoform Disorder

Thomas Probst, Heribert Sattel, Harald Gündel, Peter Henningsen, Johannes Kruse, Gudrun Schneider, Claas Lahmann

This secondary analysis of a trial on brief psychodynamic-interpersonal therapy (PIT) for patients with multisomatoform disorder investigated whether alexithymia moderates the associations between the therapeutic alliance and the outcome of PIT and whether moderating effects of alexithymia remain significant when controlling for depression. Eighty-three patients with multisomatoform disorder receiving PIT were statistically analyzed. Moderation analyses were performed with the SPSS macro PROCESS. The primary outcome (Y), self-reported physical quality of life at 9-month after the end of PIT, was measured with the physical component summary (PCS) of the SF-36 Health Survey. The potential moderator (M) alexithymia was operationalized with the Toronto Alexithymia Scale (TAS-20) at pre-treatment and the predictor (X) the therapeutic alliance was rated by both patients and therapists via the Helping Alliance Questionnaire (HAQ) at the end of PIT. Moreover, the PCS at pre-treatment functioned as covariate in all moderation models. When the patients' alliance ratings were analyzed, alexithymia did not moderate associations between the alliance and the outcome. When the therapists' alliance ratings were evaluated, alexithymia moderated the relationship between the alliance and the outcome (p < 0.05): a stronger alliance in the therapists' perspective was beneficial for the outcome only for patients scoring above 61 on the TAS-20. This moderating effect of alexithymia was, however, not statistically significant anymore when adding the pre-treatment depression scores (PHQ-9) as a covariate to the moderation model. The results underline the importance of a good therapists' view of the alliance when treating alexithymic patients and highlight the complex interaction between alexithymia and depression. Future studies are needed to extend the scope of research regarding which psychotherapeutic mechanisms of change are beneficial for which patients.