Supplementary Material for: Effects of Psychotherapy on DNA Strand Break Accumulation Originating from Traumatic Stress

<b><i>Background:</i></b> Previous research reveals an association between traumatic stress and an increased risk for numerous diseases, including cancer. At the molecular level, stress may increase carcinogenesis via increased DNA damage and impaired DNA repair mechanisms. We assessed DNA breakage in peripheral blood mononuclear cells from individuals with post-traumatic stress disorder (PTSD) and measured the cellular capacity to repair single-strand breaks after exposure to ionizing X-radiation. We also investigated the effect of psychotherapy on both DNA breakage and DNA repair. <b><i>Methods:</i></b> In a first study we investigated DNA breakage and repair in 34 individuals with PTSD and 31 controls. Controls were subdivided into 11 trauma-exposed subjects and 20 individuals without trauma exposure. In a second study, we analysed the effect of psychotherapy (Narrative Exposure Therapy) on DNA breakage and repair. Thirty-eight individuals with PTSD were randomly assigned to either a treatment or a waitlist control condition. Follow-up was performed 4 months and 1 year after therapy. <b><i>Results:</i></b> In study 1 we found higher levels of basal DNA breakage in individuals with PTSD and trauma-exposed subjects than in controls, indicating that traumatic stress is associated with DNA breakage. However, single-strand break repair was unimpaired in individuals with PTSD. In study 2, we found that psychotherapy reversed not only PTSD symptoms, but also DNA strand break accumulation. <b><i>Conclusion:</i></b> Our results show - for the first time in vivo - an association between traumatic stress and DNA breakage; they also demonstrate changes at the molecular level, i.e., the integrity of DNA, after psychotherapeutic interventions.

**研究背景：** 既往研究表明，创伤性应激与包括癌症在内的多种疾病的患病风险升高存在关联。在分子层面，应激可通过加剧DNA损伤、削弱DNA修复机制促进癌变。本研究对创伤后应激障碍（post-traumatic stress disorder, PTSD）患者外周血单个核细胞的DNA断裂情况进行了评估，并检测其在暴露于电离X射线后修复单链断裂的细胞能力；此外还探讨了心理治疗对DNA断裂及DNA修复的影响。

**研究方法：** 第一项研究纳入34名PTSD患者与31名对照个体，对其DNA断裂与修复情况进行检测。对照个体进一步分为11名有创伤暴露史者与20名无创伤暴露史者。第二项研究分析了心理治疗（叙事暴露疗法，Narrative Exposure Therapy）对DNA断裂与修复的影响，将38名PTSD患者随机分配至治疗组与等待名单对照组，分别于治疗后4个月与1年开展随访。

**研究结果：** 第一项研究结果显示，PTSD患者与有创伤暴露史者的基础DNA断裂水平均高于对照个体，表明创伤性应激与DNA断裂存在关联；但PTSD患者的单链断裂修复能力并未受损。第二项研究结果表明，心理治疗不仅能够改善PTSD症状，还可逆转DNA链断裂的蓄积情况。

**研究结论：** 本研究结果首次在体内环境中证实了创伤性应激与DNA断裂之间的关联，同时还揭示了心理干预后分子层面（即DNA完整性）的变化。