A Multi-Sample Confirmatory Factor Analysis of PTSD Symptoms

What Exactly Is Wrong with the DSM-IV Structure?

Published in: Clinical Psychology Review, v. 33, no. 1, Feb. 2013, p. 54-66

Posted on RAND.org on December 28, 2012

by Grant N. Marshall, Terry L. Schell, Jeremy N. V. Miles

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Within the DSM-IV, PTSD symptoms are rationally classified as assessing one of three symptom domains: reexperiencing, avoidance/numbing, or hyperarousal. However, two alternative four-factor models have been advocated as superior to the DSM-IV framework, based on confirmatory factor analysis. In the Numbing model, symptoms of emotional numbing are differentiated from avoidance. In the Dysphoria model, several symptoms of numbing and hyperarousal are combined to form a factor purported to assess general psychological distress. Examination of these models, within 29 separate data sets, supports two conclusions. First, contrary to its conceptual underpinnings, the Dysphoria model differs empirically from the Numbing model solely in the correlation predicted between two hyperarousal symptoms; all other predicted correlations made by the two models are substantively identical. Second, when the factor analytic presumption of simple structure is relaxed to allow for potential presentation order effects, other plausible symptom structures emerge. In particular, the fit of the DSM-IV model improved dramatically and was a better fit to the data than either four-factor model. The ostensible inferiority of the DSM-IV model may be due to a methodological artifact stemming from the order in which symptoms are typically assessed. The provisional decision to revise the structure of PTSD symptoms in the DSM-5 in light of confirmatory factor analytic results may be misguided.

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