Online Intensive Short-Term Dynamic Psychotherapy for Treatment-Resistant Somatic Symptom Disorder: An Interrupted Time-Series Study

Abstract

Abstract – Introduction: Somatic symptom disorder (SSD) is associated with substantial impairment and high healthcare use, particularly among patients with chronic symptoms, psychiatric comorbidity, and poor response to standard interventions. Intensive short-term dynamic psychotherapy (ISTDP) is a promising emotion-focused approach, but evidence in treatment-resistant SSD remains limited. Methods: In this interrupted time-series study, 25 SSD patients who showed no improvement across two empirically supported online interventions in the preceding project year received up to 16 sessions (M = 14.1) of online ISTDP. Piecewise multilevel modeling compared PHQ-15 trajectories across 60 weeks before and 21 weeks after start of ISTDP. Secondary measures (PHQ-9, GAD-7, PCL-5, DERS-16) were administered pre-, post-, and at 12-week follow-up. Results: PHQ-15 trajectories were stable or slightly worsening during the pretreatment year but declined significantly after ISTDP began, corresponding to a large estimated slope difference (d = 1.08) at the end of the treatment phase. Among completers (n = 22), 59% achieved minimal clinically meaningful improvement (≥3 PHQ-15 points), 27% showed ≥30% reduction, and 14% met recovery criteria. Secondary outcomes showed significant pre-post improvements in depression (d = 0.68) and anxiety (d = 0.42), while trauma symptoms and emotion regulation showed small, non-significant changes (d ≤ 0.30). Gains were largely maintained at 12-week follow-up. Emotional responses to treatment were common, but serious adverse events rare and dropout low. Conclusions: Online ISTDP appears feasible and effective for SSD patients who do not benefit from lower intensity interventions and may represent a useful next step in stepped-care pathways for complex, treatment-resistant presentations.