Crossover between diagnostic and empirical categorizations of full and subthreshold PTSD.

Most of the work on understanding subthreshold PTSD has focused on inconsistencies in defining subthreshold PTSD and how those inconsistencies impact prevalence rates. The present study distinguishes between full and subthreshold PTSD using empirical categorization and assesses the circumstances under which empirical categorization is discordant with full and subthreshold PTSD diagnoses.

Using data from the NIDA Clinical Trials Network protocol “Women’s Treatment for Trauma and Substance Use Disorders” (CTN-0015), researched used a modernized adaptation of the Jacobson and Truax (1991) framework, assessing whether patients were above or below an empirical threshold on latent PTSD severity scores estimated under categorical confirmatory factor analysis; the empirical categorizations were then crossed with the diagnosis to form four diagnostic by empirical categorization groupings.

Compared to a reference group (full PTSD diagnosis and empirical categorization), patients who had a full PTSD diagnosis but a subthreshold empirical categorization had lower symptom endorsement rates on 15 PTSD symptoms, were more likely to be married, ethnic minorities with fewer lifetime traumas. Conversely, patients with a subthreshold PTSD diagnosis and a full PTSD empirical grouping looked similar to “Full/Fulls,” only differing on avoidance symptoms.

Conclusions: Although alternative definitions of subthreshold PTSD and coding of symptom endorsement, as well as use of DSM-IV symptoms (though reconciled against overlapping symptoms from DSM-5), may impact results, these results suggest that empirical categorization can be a useful supplement to diagnosis in distinguishing subthreshold PTSD from full PTSD, using a methodology that could provide a platform for melding dimensional and categorical nosology approaches in the DSM.

Related protocols: CTN-0015