Typologies of Combat Exposure and Their Effects on Posttraumatic Stress Disorder and Depression Symptoms.

The present study identified distinct classes of U.S. military service members based on their combat experiences and examined mental health outcomes and longitudinal growth curves of posttraumatic stress disorder (PTSD) and depression symptoms associated with each class. Participants were 551 active duty service members who screened positive for PTSD and/or depression based on DSM-IV-TR criteria. All participants completed the Combat Experiences Scale at baseline as well as PTSD and depression measures at baseline and at 3-, 6-, and 12-month follow-ups. A latent class analysis identified four classes of service members based on their combat experiences: limited exposure, medical exposure, unit exposure, and personal exposure. Service members in the personal exposure class were characterized by a distinct mental health profile: They reported a higher level of PTSD symptoms at baseline and a higher prevalence of traumatic brain injury and PTSD diagnoses during the course of the study. The limited exposure class was more likely to receive diagnoses of depression and adjustment disorders. All classes except the medical exposure class demonstrated a slight decrease in PTSD and depression symptoms over time. However, participants in the limited exposure class had a larger decrease in PTSD and depression symptoms earlier in care but did not demonstrate superior long-term symptom improvements at 12 months compared to the other groups. These results inform PTSD development models and have implications for the screening and clinical management of combat-exposed service members.