Inclusion Criteria:
1. Active duty uniformed SM or Veteran who is currently eligible for treatment at WRNMMC (i.e., Defense Enrollment Eligibility Reporting System (DEERS)-eligible).
2. Ability to read, write, and speak English.
3. Ability to provide informed consent.
4. NICoE Intensive Outpatient Program (IOP) or NatHx Study comprehensive evaluation ≥3 years prior to current evaluation with valid neuropsychological test results.
5. Consent to allow access to prior research data collected through the NICoE TBI Neuroimaging Core Project or NatHx Study and consent to allow access to at least 1 prior blood specimen previously collected through these studies or the DoD Serum Biorepository.
Additional TBI Inclusion Criteria
1\. History of at least one mild, moderate, severe, or penetrating TBI \> 3 years prior to enrollment. TBI will be diagnosed if any one of the following criteria immediately after the injury is met and attributed to the brain injury, rather than environmental/psychological/other injury factors (DoD-VA criteria246):
1. Loss of consciousness (LOC) or post-traumatic amnesia (PTA)
2. Alteration of consciousness (AOC)
3. Evidence of neurologic dysfunction
4. TBI-related abnormality on structural neuroimaging (either CT or MRI). Additional Healthy Control Criteria
1. History of military deployment.
2. Low history of blast exposure (i.e., \<10 blasts) Additional Blast Control Criteria
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1. History of significant blast exposure (i.e., exposure to ≥ 10 blasts)
Exclusion Criteria:
1. Disabling neurologic or psychological disorders such as autism, cerebral palsy, developmental disorder, stroke, brain tumor, multiple sclerosis, meningitis, encephalitis, brain abscess, vascular malformation, pre-injury epilepsy, schizophrenia, bipolar disorder, personality disorder
2. Diabetes mellitus requiring drug treatment
3. Hypertension requiring more than 1 antihypertensive drug to control BP
4. History of myocardial infarction or other systemic vasculopathies
5. Dementia diagnosis at initial NICoE/NatHx Study assessment
