The Brain Injury Outcomes (BIO) Study is a longitudinal study with the short-term objective of better characterizing multi-modal outcomes in individuals who have sustained a brain injury using a systems medicine approach. Long-term aims include monitoring participants for signs of emerging symptoms or age-related vulnerabilities. Identification of abnormality profiles for all severity levels of brain injury (from any source) reflects a second long-range goal. Third, the investigators will examine and compare physiology between Veterans who have sustained a Mild Traumatic Brain Injury (mTBI) with and without persisting symptoms and various co-morbidities including posttraumatic stress disorder (PTSD). A control group of Veterans who have not sustained a TBI will also be recruited for comparison. Fourth, the investigators intend to facilitate the clinical use of advanced methodologies, such as brain imaging and tissue measures, with the brain injured (and other populations). Finally, the investigators will assess methods of analysis, combination and integration for multi-modal data in search of diagnostic profiles. Increased knowledge of injury patterns and the trajectory associated with brain injury could contribute to better methods of diagnosis, monitoring and, perhaps, treatment.