Can changes in multidimensional self-reported interoception be considered as outcome predictors in severely depressed patients? A moderation and mediation analysis.

Objective: Somatic complaints (e.g. pain) and abnormal self-reported interoception (e.g. maladaptive bodily self-focus) are common features of major depressive disorder (MDD) with sex-specific manifestations. Whereas somatic symptoms are associated with adverse clinical outcomes (e.g. residual symptoms), studies are scarce investigating the role of interoception as an outcome predictor for specific hospital treatment of MDD. Therefore, multivariate associations between changes in multidimensional self-reported interoception, somatic symptoms, and clinical improvements are explored by hypothesizing interactions with sex and an interoceptive mechanism.

Methods: In this naturalistic study, 87 hospitalized participants suffering from MDD completed questionnaires at pre- and post-treatment assessing multidimensional self-reported interoception (MAIA-2), somatic symptom burden (SCL-90-S® SOMA), and depression severity (BDI-II). We performed a multiple hierarchical regression analysis to test for interaction effects. The mediation hypothesis was path-analytically tested in a parallel mediation model by bootstrapping confidence intervals for (in)direct effects.

Results: Improvements in self-reported interoception independently predicted positive treatment response, ΔR=8.61%, ΔF(8, 74) = 3.23, p < .01. Prediction effects were moderated by sex, ΔR=5.54%, ΔF(8, 66) = 2.22, p < .05. Post-hoc analyses revealed significant effects of body confidence in women, B = -4.26, t(28) = -2.78, p < .01, and of self-regulation in men, B = -3.21, t(17) = -2.27, p < .05. Effects of somatic symptom relief on treatment outcome were partially mediated by self-reported interoception, total indirect = 2.94 [95% BCa CI 0.99, 5.69].

Conclusion: Interoception patterns changed significantly and predicted outcome of hospital treatment in severely depressed patients. Our study could imply the need to consider body sensations additionally as a target for antidepressive treatments. The development of tailored interoceptive interventions in depressive patients represents a promising vision for the future.