Interactions between mental health predictors on post-concussive depressive symptoms among service members and...

US service members and veterans (SMVs) are at an increased risk for both concussion and mental health disorders such as depression and post-traumatic stress disorders (PTSD). Although depression history has been shown associated with elevated post-concussive depressive symptoms, it is unclear whether this relationship changes in the presence of other mental health conditions such as PTSD. This study evaluated whether the relationship between depression history and the level of post-concussive depressive symptoms varied by pre-injury PTSD.

Data from 427 SMVs with concussion history from a US military medical center was used for this cross-sectional study. Concussion, pre-injury depression, and PTSD were assessed through medical record review and self-report, and the level of post-injury depressive symptoms was measured using the Center for Epidemiologic Studies- Depression Scale. Poisson regression with robust error variance was utilized to evaluate the association of pre-injury depression with clinically-elevated depressive symptoms post-injury, and interaction by pre-injury PTSD.

Participants with (vs. without) pre-injury depression were significantly more likely to have clinically-elevated depressive symptoms post-injury, but only in the presence of pre-injury PTSD (PR = 2.02, CI = 1.45, 2.81) and not without (PR = 1.12, CI = 0.84, 1.50). Interaction by pre-injury PTSD was statistically significant (p < 0.001).

Depression history has been shown to elevate post-concussive depressive symptoms; however, the findings of this study suggest that this association may exist only in the presence of pre-injury PTSD. Identification of SMVs with concomitant depression and PTSD history may further inform the concussion treatment of those who may likely have clinically-elevated post-concussive depressive symptoms.