Causal discovery identifies posttraumatic stress as a driver of internalizing symptoms across independent veteran and civilian populations

BackgroundApproximately half of patients with posttraumatic stress disorder (PTSD) also meet criteria for internalizing disorders, yet few studies assess reciprocal longitudinal relations among these symptoms. MethodsWe used longitudinal causal discovery in a veteran cohort for hypothesis-generation about PTSD and internalizing symptom drivers (n=240), followed by hypothesis-testing in two independent civilian cohorts with similar symptom assessments over time (n=79 and n=116). ResultsIn the veteran cohort, causal discovery revealed PTSD symptoms drove internalizing symptoms, which subsequently impacted social functioning; all independent of problematic alcohol use. This replicated in treatment-seeking anxiety disorders (AD, n = 79) and substance abuse (SA, n = 116) samples with significantly better model fit for PTSD symptoms driving internalizing symptoms, versus internalizing symptoms driving PTSD symptoms (BIC change for AD sample = 175.1, p<.001; BIC change for SA sample = 571.6, p<.001). We also found better model fit with PTSD symptoms driving anxiety symptoms, versus anxiety symptoms driving PTSD symptoms (BIC change for AD sample = 71.8, p < .001; BIC change for SA sample = 568.9, p < .001). Posthoc analysis in the veteran sample revealed that hyperarousal and cognitive and affective disturbance bridged between other PTSD symptoms and internalizing symptoms. ConclusionsOur findings suggest that internalizing symptoms that emerge in the context of PTSD are more likely to be driven by PTSD symptoms. These results highlight the need for a PTSD- and trauma-informed approach to treating internalizing symptoms, and provide preliminary evidence for cognition and mood disruption as a factor driving comorbidity.