Association of blood-based glial fibrillary acidic protein level with depression and suicidal ideation following traumatic brain injury with Glasgow Coma Scale score 13 to 15: a TRACK-TBI study

Blood-based glial fibrillary acidic protein (GFAP) level within 24 h of traumatic brain injury (TBI) has been inversely associated with post-traumatic stress disorder at 6 months in the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study. We sought to assess the relationship between day-of-injury GFAP and cumulative prevalence (CI) of depression or suicidal ideation in the first year after injury among patients presenting with Glasgow Coma Scale 13-15 who participated in Transforming Research and Clinical Knowledge in Traumatic Brain Injury (<i>n</i> = 1511). Multivariable logistic regression models were used to assess the association of day-of-injury GFAP levels with year 1 CI of depression or suicidal ideation adjusting for age, sex, prior TBI, psychiatric history and acute intracranial trauma on head computed tomography (CT) scan. Subgroup analyses categorized into 'high' and 'low' risk for mental health problems based upon a history of psychiatric disorder or TBI. Overall, 20.4% reported depression and 11.3% reported suicidal ideation in the first year. Participants with depression had significantly lower GFAP compared with participants without depression overall (median = 149.9 pg/mL versus 306.9 pg/mL, <i>P</i> < 0.001) and CT-negative high risk and CT-negative low risk subgroups. Participants with suicidal ideation had lower GFAP in the overall sample (155.8 pg/mL versus 299.1 pg/mL, <i>P</i> = 0.001). We found an interaction between GFAP and CT status, reflecting an inverse association of GFAP with cumulative depression among CT- subjects (adjusted odds ratio = 0.84, 95% CI: 0.77-0.92), but not among CT+ subjects. Blood biomarkers may warrant future investigation as potential predictors of depression following TBI in patients without evidence of acute intracranial trauma on CT scan.