Core Outcome Domains for Clinical Trials on Somatic Symptom Disorder, Bodily Distress Disorder, and Functional Somatic Syndromes: European Network on Somatic Symptom Disorders Recommendations.

Objective: The harmonization of core outcome domains in clinical trials facilitates comparison and pooling of data, and simplifies the preparation and review of research projects and comparison of risks and benefits of treatments. Therefore, we provide recommendations for the core outcome domains that should be considered in clinical trials on the efficacy and effectiveness of interventions for somatic symptom disorder, bodily distress disorder, and functional somatic syndromes.

Methods: The European Network on Somatic Symptom Disorders group of more than 20 experts in the field met twice in Hamburg to discuss issues of assessment and intervention research in somatic symptom disorder, bodily distress disorder, and functional somatic syndromes. The consensus meetings identified core outcome domains that should be considered in clinical trials evaluating treatments for somatic symptom disorder and associated functional somatic syndromes.

Results: The following core domains should be considered when defining ascertainment methods in clinical trials: a) classification of somatic symptom disorder/bodily distress disorder, associated functional somatic syndromes, and comorbid mental disorders (using structured clinical interviews), duration of symptoms, medical morbidity, and prior treatments; b) location, intensity, and interference of somatic symptoms; c) associated psychobehavioral features and biological markers; d) illness consequences (quality of life, disability, health care utilization, health care costs; e) global improvement and treatment satisfaction; and f) unwanted negative effects.

Conclusions: The proposed criteria are intended to improve synergies of clinical trials and to facilitate decision making when comparing different treatment approaches. These recommendations should not result in inflexible guidelines, but increase consistency across investigations in this field.