OBJECTIVE: Somatic symptom disorder (SSD) is commonly encountered in health care settings. Cognitive-behavioural treatments have been most extensively studied, but they tend to have small effects of temporary duration. Emotional awareness and expression therapy (EAET) is a newly developed treatment for SSD, targeting emotional processing of trauma and conflict as a mechanism of symptom change. In an earlier uncontrolled study of self-guided, internet-administrated EAET (I-EAET), we found substantial reductions in somatic symptoms, prompting the need for a randomized controlled trial of I-EAET.

METHODS: We conducted a 2-arm RCT, comparing 10-week I-EAET (n = 37) to a waitlist control (WL; n = 37). Primary outcomes were reductions of somatic symptoms (PHQ-15) and pain intensity (BPI-4) at post-treatment, with a 4-month evaluation of effect duration. We also analysed emotional processing (EPS-25) and depression (PHQ-9) as possible mediators of I-EAET's effects.

RESULTS: Compared to controls, I-EAET significantly reduced somatic symptoms at both post-treatment and follow-up. I-EAET also reduced pain, depression, insomnia, and anxiety at post-treatment, but these effects were not retained at follow-up. As hypothesized, a facet of emotional processing partially mediated the treatment effect on somatic symptoms, even when controlling for depression.

CONCLUSIONS: Although treatment effects were smaller than in the previous uncontrolled trial, I-EAET is a promising treatment for SSD, with a minority of patients (around 20%) experiencing substantial clinical improvement. The benefits of I-EAET are partially mediated by improved emotional processing. Future research should identify and target patients who respond best to I-EAET and develop tailored treatment to enhance treatment effects. (Preregistered at clinicaltrials.gov: NCT04751825.).