Objective: A traumatic brain injury (TBI) places individuals at high risk for developing posttraumatic stress disorder (PTSD). TBIs account for the onset of PTSD in approximately 700,000 Americans each year. Depression and post-concussive syndrome (PCS) are also common and often comorbid with PTSD. However, even in this group, there is a high-level of inter-individual response to traumatic brain injuries, suggesting that a better understanding of the mechanisms underlying this risk would be of great value in directing preventive interventions. The reasons for this heterogeneity are undoubtedly multi-factorial, and involve a complex interplay between genetic and environmental factors, that we may be able to understand through peripheral biomarkers and central examination of neuronal functioning. We suggest that DNA methylation may be a putative biomarker of psychiatric risk, as it reflects long-term changes in the function of the gene and may shape the recovery ability of the TBI patient through changes in cell function. In addition, differential proteomic response, including the function of the neuroendocrine system, likely relates to changes from epigenetic modification in both neurons and immune cells, which may contribute to the risk for the onset of PTSD as well as depression and PCS. We have previously shown that both PTSD and depression are associated with endocrine alterations, leading us to question if this biological change may underlie vulnerability for the onset of PTSD as well as depression and PCS following a TBI. In support of the idea of shared vulnerability, patients with a TBI also often display endocrine function alterations. In addition, sleep disturbance is common following TBI and is a core symptom of PTSD depression and PCS, suggesting that sleep may contribute to psychiatric and neurological recovery from a TBI. This line of research is essential, as current treatments to prevent or treat psychiatric risk following TBI are often ineffective, and even treatment of PCS is limited. This poor understanding results in our limited ability to reduce the risk for compromises in the health and well-being of patients who sustain a TBI.