Theory of mind impairment in Huntington's disease patients and their relatives

ABSTRACT Huntington disease (HD) is an autosomal dominant genetic disorder characterized by movement disorders, cognitive impairment, and psychiatric symptoms. Relatives of HD patients experience a great burden as the latter suffer from altered social conduct and deterioration of interpersonal relationships. Theory of mind (ToM) is the ability to attribute mental states (to oneself and others). Deficits in ToM are thought to have a role in the changes in empathy and interpersonal difficulties that HD patients face. Methods: We conducted a cross sectional study to compare ToM task scores of patients with mild to moderate HD, their relatives (spouse or at-risk first-degree relative with a negative gene test) and controls.Individuals with dementia or depression were excluded. The ToM test battery included Spanish versions of the Reading Mind in the Eyes Test (RMET), Happé's Strange Stories (Social and Physical Stories subtests) and the Hinting Task. Results: The series comprised 12 HD patients, 12 relatives and 12 controls. The HD patients showed lower affective ToM scores than controls (RMET 19 [3.5] vs 23.9 [2.7], p = 0.016). Cognitive ToM tasks scores were lower in HD patients than controls as well (Happé's Social Stories 9 [2.6] vs 13 [1.9], p = 0.001; the Hinting Task 13.6 [3.4] vs 17.5 [4.0], p = 0.009). In the Hinting Task, HD relatives had lower scores in than controls (13 [3.2] vs 17.5 [4.0], p = 0.009) and similar scores to controls in the rest of the battery. Conclusion: The HD patients with mild to moderate disease severity and their relatives show ToM deficits.摘要 亨廷顿舞蹈症（Huntington disease, HD）是一种常染色体显性遗传性疾病，以运动障碍、认知功能损害及精神症状为核心特征。HD患者会出现社交行为改变与人际关系恶化，其亲属因此承受沉重照料与心理负担。心理理论（Theory of Mind, ToM）指个体对自身及他人心理状态进行归因的能力，学界普遍认为心理理论缺损与HD患者的共情能力改变及人际困境密切相关。方法：本研究开展横断面研究，对比轻中度HD患者、其亲属（配偶或基因检测阴性的高危一级亲属）与健康对照的心理理论任务得分，排除合并痴呆或抑郁的受试者。心理理论测试组合包含西班牙语本地化版本的眼神读心测试（Reading Mind in the Eyes Test, RMET）、Happé奇异故事测验（分为社会故事与物理故事两个子测验）以及暗示任务（Hinting Task）。结果：本研究共纳入12名HD患者、12名患者亲属及12名健康对照。轻中度HD患者的情感性心理理论得分低于对照组（眼神读心测试得分：19[3.5] vs 23.9[2.7]，p=0.016）。HD患者的认知性心理理论任务得分同样显著低于对照组（Happé社会故事测验得分：9[2.6] vs 13[1.9]，p=0.001；暗示任务得分：13.6[3.4] vs 17.5[4.0]，p=0.009）。在暗示任务中，HD患者亲属的得分低于对照组（13[3.2] vs 17.5[4.0]，p=0.009），其余测试项目得分与对照组无显著差异。结论：轻中度HD患者及其亲属均存在心理理论缺损。