Resonant breathing in hospitalised psychiatric patients with persistent somatic symptoms: a randomised controlled trial.

Background: Persistent somatic symptoms are a common feature in many psychiatric disorders. Moderate-to-severe cases often necessitate treatment in specialised inpatient psychiatric settings. Aims: This study evaluated the efficacy, safety and acceptability of resonant breathing (personalised slow breathing to maximise heart rate variability (HRV)) as adjunctive treatment for hospitalised patients with psychiatric disorders presenting with persistent somatic symptoms on admission, when patients typically present with high symptom severity. Methods: This multicentre, randomised, placebo-controlled cross-over study included 78 patients diagnosed with somatic symptom disorder or affective disorders with persistent somatic symptoms. Participants underwent light-guided resonant breathing and sham light therapy two times per day for 5 weekdays each, starting an average of 11 days after admission. The primary outcomes were changes in self-reported somatic well-being and arousal (efficacy), and adverse effects (safety). Secondary outcomes included somatic, anxiety, depression and insomnia symptoms, HRV measures and patient satisfaction (acceptability). The trial was preregistered in the German Clinical Trial Register (ID: DRKS00027323) and funded by the Austrian Research Promotion Agency (Grant ID. F0999886082). Results: Resonant breathing rates were six breaths per minute in 60% of patients and higher in the remaining participants. The study found no intervention-specific effect on primary outcomes of self-reported somatic well-being and arousal. Patients reported no adverse effects and expressed high satisfaction with the breathing intervention. Resonant breathing significantly reduced secondary outcomes of self-reported anxiety (η²p=0.09, 95% CI 0.01 to 0.22) and insomnia symptoms (η²p=0.10, 95% confidence interval (CI) 0.01 to 0.23) after 10 sessions. It also significantly improved several HRV measures acutely (η²p range: 0.23 (95% CI 0.09 to 0.38) to 0.51 (95% CI 0.35 to 0.62)). Conclusions: While resonant breathing did not improve somatic well-being or arousal, it was safe, well-tolerated and effective at reducing anxiety and insomnia symptoms during early hospitalisation. These findings support further investigation into resonant breathing for these specific indications over extended periods. Trial registration number: DRKS00027323.