App-Based Self-Management for Somatic Symptom Disorder and MUS: A Pilot Study

Objectives The primary objective of this study is to evaluate the effectiveness of an eight-week self-management mobile application for adults experiencing somatic symptom disorder (SSD) or medically unexplained symptoms (MUS). Improvement will be assessed using the PHQ-15. The secondary objective is to examine changes in clinical symptoms and physiological indicators following app use, as well as to assess the acceptability and usability of the intervention. Scientific Rationale Somatic symptoms without clear medical explanation account for 15-30% of primary care visits (Peveler et al., 1997; Fink et al., 1999; Ko et al., 2011). Diagnostic terminology has evolved from somatoform disorders in DSM-IV and MUS to SSD in DSM-5, which emphasizes distressing symptoms accompanied by maladaptive thoughts, emotions, or behaviors (Scott et al., 2022). SSD is frequently associated with alexithymia, emotional suppression, and difficulty regulating anger, consistent with theories of somatization as the bodily expression of unprocessed affect (Anuk \& Bahadir, 2017; Liu et al., 2011). These difficulties contribute to interpersonal impairment and excessive health care use, often resulting in frustration for clinicians (Orzechowska et al., 2020). Psychological treatments, including CBT, MBSR, MBCT, and ACT, have demonstrated efficacy in reducing symptom burden across conditions such as IBS, fibromyalgia, tinnitus, and chronic fatigue (Hauge et al., 2015; Kikuchi et al., 2020; Roland et al., 2015). These therapies share mechanisms such as enhancing mind-body awareness, reducing physiological hyperarousal, and promoting adaptive coping and acceptance (Aktas et al., 2019; Jing et al., 2019). However, barriers to dissemination remain, as patients with SSD often reject psychological explanations, engage in medical shopping, and maintain strong somatic attributions (Brown, 2007; Harris et al., 2009). Digital interventions offer a scalable solution by providing psychoeducation on mind-