title: Bifactor item response theory model of acute stress response.
abstract: BACKGROUND
  Better understanding of acute stress responses is important for revision of DSM-5. However, the latent structure and relationship between different aspects of acute stress responses haven't been clarified comprehensively. Bifactor item response model may help resolve this problem.
  
  
  OBJECTIVE
  The purpose of this study is to develop a statistical model of acute stress responses, based on data from earthquake rescuers using Acute Stress Response Scale (ASRS). Through this model, we could better understand acute stress responses comprehensively, and provide preliminary information for computerized adaptive testing of stress responses.
  
  
  METHODS
  Acute stress responses of earthquake rescuers were evaluated using ASRS, and state/trait anxiety were assessed using State-trait Anxiety Inventory (STAI). A hierarchical item response model (bifactor model) was used to analyze the data. Additionally, we tested this hierarchical model with model fit comparisons with one-dimensional and five-dimensional models. The correlations among acute stress responses and state/trait anxiety were compared, based on both the five-dimensional and bifactor models.
  
  
  RESULTS
  Model fit comparisons showed bifactor model fit the data best. Item loadings on general and specific factors varied greatly between different aspects of stress responses. Many symptoms (40%) of physiological responses had positive loadings on general factor, and negative loadings on specific factor of physiological responses, while other stress responses had positive loadings on both general and specific factors. After extracting general factor of stress responses using bifactor analysis, significant positive correlations between physiological responses and state/trait anxiety (r = 0.185/0.112, p<0.01) changed into negative ones (r = -0.177/-0.38, p<0.01).
  
  
  CONCLUSIONS
  Our results demonstrated bifactor structure of acute stress responses, and positive and negative correlations between physiological responses and stress responses suggested physiological responses could have negative feedback on severity of stress responses. This finding has not been convincingly demonstrated in previous research.
authors.affiliation: Department of Psychology, Fourth Military Medical University, Xi'an City, Shaanxi Province, PR China.
authors.forename: Yebing
authors.initials: Y
authors.lastname: Yang
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Sun
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Jiang
authors.forename: Jingjing
authors.initials: J
authors.lastname: Tang
authors.forename: Xia
authors.initials: X
authors.lastname: Zhu
authors.forename: Danmin
authors.initials: D
authors.lastname: Miao
mesh_terms: D000328:Adult; D001007:Anxiety / Q000523:psychology; D006801:Humans; D008962:Models, Theoretical; D011594:Psychometrics; D040701:Stress Disorders, Traumatic, Acute / Q000523:psychology*; D011795:Surveys and Questionnaires