Psychobiological Mechanisms in Somatic Symptom Disorder and Depressive Disorders: An Ecological Momentary Assessment Approach.

Objective: Persistent somatic symptoms cause strong impairment in persons with somatic symptom disorder (SSD) and depressive disorders (DDs). Specific negative psychological factors (NPFs), such as catastrophizing, negative affectivity, and behavioral avoidance, are assumed to contribute to this impairment and may maintain symptoms via dysregulations of biological stress systems. We examined the associations between NPF and somatic symptoms in the daily life of women with SSD or DD and investigated the mediating role of psychobiological stress responses.

Methods: Twenty-nine women with SSD and 29 women with DD participated in an ecological momentary assessment study. For 14 days, intensity of and impairment by somatic symptoms, NPF, and stress-related biological measures (cortisol, alpha-amylase) were assessed five times per day using an electronic device and saliva samples. Multilevel models were conducted.

Results: The greater the number of NPF, the higher the concurrent and time-lagged intensity of and impairment by somatic symptoms in both groups (12.0%-38.6% of variance explained; χ2(12) p < .001 for all models). NPFs were associated with higher cortisol levels in women with DD and with lower levels in women with SSD (interaction NPF by group: B = -0.04, p = .042 for concurrent; B = -0.06, p = .019 for time-lagged). In women with SSD, lower cortisol levels were associated with higher intensity at the next measurement time point (group by cortisol: B = -1.71, p = .020). No mediation effects were found.

Conclusions: NPFs may be considered as transdiagnostic factors in the development and treatment of impairing somatic symptoms. Our findings will allow the development of new treatment strategies that use ecological momentary intervention approaches focusing on NPF.