Exploratory associations with Tumor Necrosis Factor-α, disinhibition and suicidal endorsement after traumatic brain injury

Purpose: To examine the relationship of Tumor Necrosis Factor (TNF)-α to disinhibition and suicidal endorsement after traumatic brain injury (TBI). Participants: Adults with moderate to severe TBI (acute serum levels: n=. 48, n=. 543 samples; acute CSF levels: n=. 37, n=. 389 samples; chronic serum levels: n=. 48, n=. 326 samples). Main measures: TNFα levels (CSF, Serum) from time of injury to 12. months post-injury; Frontal Systems Behavior Scale - Disinhibition Subscale at 6 and 12. months post-injury; Patient Health Questionnaire at 6 and 12. months post-injury. Results: Participants with TBI had significantly higher CSF and serum TNFα levels than healthy controls (. p<. 0.05). Acute and chronic serum TNFα was significantly associated with disinhibition at 6. months post-injury (. p=. 0.009, p=. 0.029 respectively), and 6. month disinhibition was associated with suicidal endorsement at both 6 and 12. months (. p=. 0.045, p=. 0.033 respectively) and disinhibition at 12. months post-injury (. p<. 0.001). Conclusion: These preliminary data suggest a biological to behavioral pathway of suicidality after TBI, from TNFα to disinhibition to suicidal endorsement. Future investigation is warranted to validate these findings and clarify what biological mechanisms might underlie these relationships.