Supplementary Material for: Online Intensive Short-Term Dynamic Psychotherapy (ISTDP) for Treatment-Resistant Somatic Symptom Disorder: An Interrupted Time-Series Study

Background: 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 pre-treatment 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.

背景：躯体症状障碍（Somatic symptom disorder, SSD）常伴随显著功能损害与高额医疗资源消耗，尤其在存在慢性症状、精神共病且对标准干预应答不佳的患者群体中更为突出。强化短期动力心理治疗（Intensive Short-Term Dynamic Psychotherapy, ISTDP）是一种颇具前景的情绪聚焦疗法，但针对难治性SSD的相关研究证据仍较为有限。
方法：本研究为间断时间序列研究，纳入此前1年内经两项循证在线干预后仍无改善的25名SSD患者，为其提供至多16次（平均14.1次）在线ISTDP治疗。采用分段多层模型比较了ISTDP启动前60周与启动后21周的患者健康问卷-15（Patient Health Questionnaire-15, PHQ-15）得分轨迹。次要结局指标包括患者健康问卷-9（Patient Health Questionnaire-9, PHQ-9）、广泛性焦虑障碍7项量表（Generalized Anxiety Disorder 7-item Scale, GAD-7）、创伤后应激障碍检查表-5（PTSD Checklist for DSM-5, PCL-5）及情绪调节困难量表-16项版（Difficulties in Emotion Regulation Scale-16, DERS-16），分别在治疗前、治疗后及12周随访时进行评估。
结果：治疗前1年，患者的PHQ-15得分轨迹趋于稳定或略有恶化，但在ISTDP启动后出现显著下降，治疗阶段末期的斜率估计差值达1.08，属于大效应量。在完成全部治疗的患者（n=22）中，59%达到了具有临床意义的最小改善（PHQ-15得分降低≥3分），27%的得分降幅≥30%，14%符合康复标准。次要结局指标显示，抑郁（d=0.68）与焦虑（d=0.42）得分在治疗前后均出现显著改善，而创伤症状与情绪调节能力仅出现微小且无统计学意义的变化（d≤0.30）。上述获益在12周随访时基本得以维持。治疗过程中情绪反应较为常见，但严重不良事件罕见，脱落率较低。
结论：对于低强度干预无效的SSD患者，在线ISTDP兼具可行性与有效性，或可为复杂难治性病例的阶梯式治疗路径提供一项有价值的后续选择。