Structural Validity of the Tonic Immobility Scale in a Population Exposed to Trauma: Evidence from Two Large Brazilian Samples

Author(s)

Reichenheim, Michael ^[1] ; Souza, Wanderson ^[2] ; Freire Coutinho, Evandro Silva ^[3] ; Figueira, Ivan ^[4] ; Quintana, Maria Ines ^[5] ; de Mello, Marcelo Feijo ^[5] ; Bressan, Rodrigo Affonseca ^[5] ; Mari, Jair de Jesus ^[5] ; Andreoli, Sergio Baxter ^[5]

Affiliation

^[1] State Univ Rio de Janeiro UERJ, Dept Epidemiol, Inst Social Med IMS, Rio De Janeiro, RJ - Brazil

^[2] Fed Rural Univ Rio de Janeiro UFRRJ, Dept Psychol, Inst Educ, Seropedica, RJ - Brazil

^[3] Fiocruz MS, Dept Epidemiol, Natl Sch Publ Hlth ENSP, Rio De Janeiro, RJ - Brazil

^[4] Fed Univ Rio de Janeiro UFRJ, Inst Psychiat IPUB, Rio De Janeiro, RJ - Brazil

^[5] Fed Univ Sao Paulo UNIFESP, Dept Psychiat, Sao Paulo - Brazil

• Document type: Journal article
• Source: PLoS One; v. 9, n. 4 APR 18 2014.
• Web of Science Citations: 3

Abstract

Background: Tonic Immobility is a temporary state of motor inhibition in situations involving extreme fear. The first scale developed for its assessment was the 10-item Tonic Immobility Scale (TIS). However, there are still few studies on its structural (dimensional) validity. The objective of this study was to reassess the factor structure of the TIS applied to representative samples exposed to general trauma of two Brazilian mega-cities. Methods: The sample comprised 3,223 participants reporting at least one traumatic experience. In Sao Paulo (n = 2,148), a Confirmatory Factor Analysis (CFA) first tested the originally proposed two-dimensional structure. This was followed by sequential Exploratory Structural Equation Models to identify the best fitting model, and subsequently tested in Rio de Janeiro (n = 1,075) via CFA. Alternative reduced versions were further explored using the aggregate sample. Model-based Item Response Theory (IRT) location parameters were also investigated. Results: An absence of factor-based convergent and discriminant validity rejected the original proposition. However, the one-dimensional structure still held several residual correlations. Further exploration indicated the sustainability of reduced versions with seven (alternative A) and six (alternative B) items. Both presented excellent fit and no relevant residual item correlation. According to the IRT location parameters, items in alternative B covered a wider range of the latent trait. The Loevinger's H scalability coefficients underscored this pattern. Conclusions: The original model did not hold. A one-factor solution was the most tenable in both large samples, but with significant item residual correlations, indicating that content redundancies persisted. Further reduced and simplified versions of the TIS proved promising. Although studies are yet to be carried out in other settings, it is the authors' impression that the restricted versions of the TIS are already apt for use in epidemiologic studies since the pros tend to outweigh the cons (as outlined in the Discussion section). (AU)

• FAPESP's process: 04/15039-0 - Post-traumatic stress disorder: epidemiology, physiopathology and treatment
• Grantee: Jair de Jesus Mari
• Support Opportunities: Research Projects - Thematic Grants