The Relationship Between Course of PTSD Symptoms in Deployed U.S. Marines and Degree of Combat Exposure

Abstract

Large cohort studies suggest that most military personnel experience minimal posttraumatic stress disorder (PTSD) symptoms following warzone deployment, an outcome often labeled resilience. Very low symptom levels, however, may be a marker for low exposure, not resilience, which requires relatively high-magnitude or high-frequency stress exposure as a precondition. We used growth mixture modeling (GMM) to examine the longitudinal course of lifetime PTSD symptoms following combat exposure by disaggregating deployed U.S. Marines into upper, middle, and lower tertiles of combat exposure. All factor models fit the data well; Tucker-Lewis Index (TLI) and comparative fit index (CFI) values ranged from .91 to .97. Three distinct trajectories best explained the data within each tertile. The upper tertile comprised True Resilience (73.2%), New-Onset Symptoms (18.3%), and Pre-existing Symptoms (8.5%) trajectories. The middle tertile also comprised True Resilience (74.5%), New-Onset Symptoms (16.1%), and Pre-existing Symptoms (9.4%) trajectories. The lower tertile comprised Artifactual Resilience (86.3%), Pre-existing Symptoms (7.6%), and New-Onset Symptoms (6.1%) trajectories. True Resilience involved a clinically significant symptom increase followed by a return to baseline, whereas Artifactual Resilience involved consistently low symptoms. Conflating artifactual and true resilience may inaccurately create the expectation of persistently low symptoms regardless of warzone exposure.

Susceptibility and Resilience to Posttraumatic Stress Disorder–like Behaviors in Inbred Mice

“…We had no prior history of collaboration with the latter, located at Rutgers University. Using an electronic copy of the protocol, the TSRI Behavior Core (Supplementary Figure S5, top) and Shumyatsky Laboratory (Supplementary Figure S5, bottom) obtained results similar to core features seen by our group: (1) relationship between FC training and extinction specific to stress+FC males (TSRI FC Pearson=0.245, p=0.38; stress+FC=0.319, p=0.05; Shumyatsky FC Pearson=0.539, p=0.21, stress+FC=0.679, p=0.004; Supplementary Figure S5B, D, G, I); (2) segregation of the stress+FC, but not FC, population into SS and SR phenotypes (RM-ANOVA TSRI stress+FC: interaction F (1,36) =5.07, p=0.031; Shumyatsky stress+FC: interaction F(1,14)=10.56, p=0.006, Supplementary Figure S5E,J); and (3) higher freezing in SS relative to FC (RM-ANOVA SS vs FC, TSRI: interaction F (1,28) =2.51, p=0.124; Shumyatsky: interaction F (1,11) =15.99, p=0.002, Supplementary Figure S5E,J). …”

“…A history of stress increases the likelihood of developing post-traumatic stress disorder (PTSD) (1, 2), defined by persistent recollections of a trauma, with hyperarousal, avoidance of trauma-related cues and negative changes in mood and cognition (3). Antidepressants, the only FDA-approved pharmaceutical for PTSD, have limited efficacy over placebo and low remission (4, 5).…”

Expression and methylation in posttraumatic stress disorder and resilience; evidence of a role for odorant receptors

“…A recent analyses of PTSD versus non-PTSD or resilient outcomes in deployed military personnel implicated degrees of trauma exposure as a factor determining PTSD (Boasso et al, 2015). Thus the degree of trauma exposure could confound case control studies of PTSD even when controls are defined as trauma exposed.…”

Fear response-based prediction for stress susceptibility to PTSD-like phenotypes

“…Posttraumatic stress disorder (PTSD) is a mental disorder triggered by exposure to traumatic stresses. PTSD is distinguished from other stress-induced disorders, including depression, schizophrenia, and general anxiety disorder, and thus was separately listed in the 5th edition of the Diagnostic and Statistical Manual (DSM-5) [1][2][3]. A characteristic symptom of PTSD is persistent reexperiencing or dreaming of traumatic episode(s), and the patients also exhibit fear generalization, exemplified by hypervigilance and exaggerated responses toward potential threats and even irrelevant cues [3,4].…”