Design: This is a natural history study that will recruit patients within 30 days of a mild/moderate TBI, and will follow them over a one year period, with follow-up at 1, 3, 6 and 12 months following the TBI. Biological profiles including the concentration of inflammatory proteins and neuropeptides, and DNA methylation will be examined. An optional structural and functional magnetic resonance imaging (fMRI), and a hydrocortisone stimulation test will be used to evaluate the role of neuronal and neuroendocrine functioning following TBI.