• Active duty uniformed SM or Veteran who is currently eligible for treatment at WRNMMC (i.e., Defense Enrollment Eligibility Reporting System (DEERS)-eligible).

• Ability to read, write, and speak English.

• Ability to provide informed consent.

• NICoE Intensive Outpatient Program (IOP) or NatHx Study comprehensive evaluation ≥3 years prior to current evaluation with valid neuropsychological test results.

• 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):

• Loss of consciousness (LOC) or post-traumatic amnesia (PTA)

• Alteration of consciousness (AOC)

• Evidence of neurologic dysfunction

• TBI-related abnormality on structural neuroimaging (either CT or MRI). Additional Healthy Control Criteria

‣ History of military deployment.

⁃ Low history of blast exposure (i.e., \<10 blasts) Additional Blast Control Criteria

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‣ History of significant blast exposure (i.e., exposure to ≥ 10 blasts)