Longitudinal patterns of PTSD symptom classes among US National Guard service members during reintegration.

Purpose: The purpose of this study was to identify posttraumatic stress disorder (PTSD) symptom groups and assess their longitudinal progression during their first year of reintegration among United States (US) National Guard (NG) service members.

Methods: A cohort of NG service members (n = 886) completed surveys at 6 and 12 months following their return from deployment to Iraq or Afghanistan. Latent class analysis (LCA) and latent transition analysis (LTA) were used to empirically derive groups based on their PTSD symptoms and examine their longitudinal course, respectively.

Results: The best fitting model at both assessments was the four-class model, comprising an asymptomatic class (6 months = 54%; 12 months = 55%), a mild symptom class with elevated hyperarousal symptoms (6 months = 22%; 12 months = 17%), a moderate symptom class (6 months = 15%; 12 months = 15%), and a severe symptom class (6 months = 10%; 12 months = 13%). Based on LTA, stability of class membership at the two assessments was 0.797 for the asymptomatic class, 0.453 for the mild class, 0.560 for the moderate class, and 0.580 for the severe class. Estimated transition probabilities were greater with respect to transitioning to less severe, rather than more severe, classes over time.

Conclusions: The four latent PTSD classes were distinguished primarily by severity; however, the mild symptom class was characterized by higher levels of hyperarousal than other symptoms. Although the absolute number of individuals within classes remained fairly constant between 6 and 12 months, there was movement between severity classes. Most NG service members without symptoms continued to do well during the first year, with only an estimated 7% moving to the moderate or severe class.