Modifiable Factors for Somatic Symptom Persistence in Patients with Somatic Symptom Disorder
Somatic symptom disorder (SSD) is a distressing mental disorder characterised by the presence of at least one persistent somatic symptom and a significant psychological burden due to excessive thoughts, feelings, or behaviours related to somatic symptoms or associated health concerns. Current aetiological models of SSD construe expectations both as predisposing and as maintaining factors. However, the prospective influences of patients’ expectations as potentially modifiable factors of somatic symptoms and their interaction with other relevant factors such as somatic comorbidity have not been studied.
This proposed study aims to investigate multivariable prediction models for somatic symptom persistence in patients with SSD. We hypothesise that patients’ expectations of symptom severity and different levels of somatic comorbidity are associated with somatic symptom severity. Furthermore, we hypothesise that these two factors independently or cojointly with other pre-specified biomedical and psychosocial factors such as prior treatment experience determine the long-term symptom course on a 12 months macro level and that they are predictive of daily fluctuations of somatic symptoms severity on a 10-day micro level. Exploratively, we will analyse the impact of different expectation measures as well as mediators of the proposed impact of somatic comorbidity.
This is a prospective, single-centre cohort study of somatic symptom severity as primary outcome in N=240 patients with SSD over one year with an embedded ecological momentary 10-day assessment of daily symptom fluctuation. Expectation measures inlcude repeated assessments of explicit expectations using two different frames of reference on the micro level as well as exploratory implicit expectation measures. Somatic comorbidity will be measured via standardised ratings, medical records, and medical exams that are performed by study physicians. Multivariable prediction models with hierarchical mixed models will be used to examine the influence of expectations and somatic comorbidity on symptom severity as primary outcome on the micro level. On the micro level, hypothesis regarding daily symptom fluctuations will be anaylsed using multivariable latent growth curve models.
To our knowledge, this is the first investigation of the roles and temporal impacts of expectations as modifiable determinants of somatic symptom severity in patients with SSD. The in-depth analyses of macro level symptom course and micro level fluctuations of symptom severity, while simultaneously considering the role of somatic comorbidity and other biomedical and psychological factors, will render clinically relevant conclusions regarding future targeted treatment options. Furthermore, we will draw conclusions regarding the utility of somatic comorbidity as a potential diagnostic specifier for SSD.