Based on the premise that treatment changes people in ways that are consequential for subsequent treatment-seeking, we question the validity of an unrecognized and apparently inadvertent assumption in mental health services research conducted within a psychiatric epidemiology paradigm. This homogeneity assumption statistically constrains the effects of potential determinants of recent treatment to be identical for former patients and previously untreated persons by omitting treatment history or modeling only main effects. We test this assumption with data from the 2001–2003 Collaborative Psychiatric Epidemiology Surveys; the weighted pooled sample is representative of noninstitutionalized U.S. adults (18+; analytic n = 19,227). Contrary to the homogeneity assumption, some associations with recent treatment are conditional on past treatment, including psychiatric disorder and race-ethnicity—measures of need and treatment disparities, respectively. We conclude that the widespread application of the homogeneity assumption probably masks differences in the determinants of recent use between previously untreated persons and former patients.

中文翻译：

---

新移民和老朋友：精神卫生服务研究中的错误假设

基于治疗会以随后的寻求治疗的方式改变人们的前提，我们质疑在精神病学流行病学范式下进行的精神卫生服务研究中一个未被认识的，显然是无意的假设的有效性。该均一性假设通过省略治疗历史或仅对主要作用进行建模，从而从统计学上将近期治疗的潜在决定因素的影响限制在以前的患者和以前未治疗的患者相同。我们用2001-2003年合作精神病流行病学调查的数据检验了这一假设；加权合并样本代表了非机构化的美国成年人（18岁以上；分析n = 19,227）。与同质性假设相反，与近期治疗相关的某些条件取决于过去的治疗方法，包括精神疾病和种族民族-分别衡量需求和治疗差异的方法。我们得出结论，同质性假设的广泛应用可能掩盖了先前未治疗的人和以前的患者之间最近使用的决定因素的差异。