Somatic symptom disorder in patients with irritable bowel syndrome or ulcerative colitis - Cross-sectional baseline findings from the SOMA.GUT-RCT.

BACKGROUND

Somatic symptom disorder (SSD) is characterised by distressing somatic symptoms accompanied by excessive symptom-related thoughts, emotions, or behaviour. While initial evidence supports SSD's relevance in gastrointestinal conditions like irritable bowel syndrome (IBS) and ulcerative colitis (UC), structured interview-based data are lacking. This study examined SSD frequency and its associations with biopsychosocial variables in patients with IBS or UC recruited in the context of a psychological intervention trial.

METHODS

Cross-sectional baseline data from a randomised controlled trial of patients with UC or IBS were analysed. SSD was diagnosed using structured DSM-5-based diagnostic interviews. Measures included illness-related anxiety (WI-7), neuroticism (BFI-10), illness perceptions (B-IPQ), symptom-related disability (adapted PDI), and gastrointestinal symptom severity (IBS-SSS). Between-group comparisons and multiple logistic regression analysis were conducted.

RESULTS

SSD was diagnosed in 41.5 % (95 % CI 35.6-47.9) out of 236 patients, including 125 patients with UC and 111 with IBS (73.7 % female; Mage = 40.14, SD = 13.8). SSD was more frequent in IBS (55.0 %; 95 % CI 44.4-64.9) than in UC (29.6 %; 95 % CI 21.7-37.1) (χ2(1) = 15.67, p < .001), and linked to higher illness-related anxiety, negative illness perceptions, and symptom-related disability in both groups. Gastrointestinal symptom severity was highest in patients with IBS and SSD. Regression analysis showed IBS diagnosis, illness-related anxiety, and neuroticism correlated with SSD.

CONCLUSIONS

A substantial number of patients with IBS or UC met SSD criteria in structured interviews. SSD occurred more commonly in IBS and was associated with psychological distress in both conditions. Findings highlight SSD's diagnostic relevance in functional and inflammatory bowel diseases. Future studies should investigate whether targeted SSD diagnosis and treatment in these conditions could improve clinical outcomes.