The relations between C-reactive protein and trauma exposure, PTSD and depression symptoms, and PTSD psychotherapy treatment response in treatment seeking veterans and service members

•There is a lack of research investigating CRP and PTSD psychotherapy response.•In a large veteran sample CRP was not associated with PTSD or depression severity.•CRP was also not associated with PTSD psychotherapy response. While inflammatory markers have been implicated in the link between PTSD and poor health outcomes, there is a paucity of research investigating C-reactive protein (CRP) and psychotherapy treatment response for posttraumatic stress disorder (PTSD). The present study utilized a large, well-characterized sample of veterans and service members (N = 493) engaged in intensive psychotherapy to investigate the associations between CRP, trauma exposure, related variables, and PTSD and depression, as well as investigating if CRP was associated with PTSD psychotherapy treatment response. Bivariate correlation results indicate that CRP was significantly associated with BMI (r = 0.48) and severity of experiences of childhood physical and sexual abuse (r = 0.14 and 0.15, respectively) and was not significantly associated with baseline PTSD total symptom severity, PTSD symptom clusters, or depression symptom severity (rs ranging from -0.03 to 0.04). In multivariate regression models investigating if CRP and related variables were associated with PTSD baseline symptom severity, CRP was not a significant predictor (β = -0.03). Hierarchical linear modeling did not identify CRP as a significant predictor of PTSD psychotherapy outcome. Given that findings indicate that CRP was broadly elevated in this treatment seeking sample but not associated with PTSD and depression symptom severity, results suggest CRP may not be a specific biomarker for PTSD or depression but may be elevated in psychiatric disease more generally.