Abstract: The invention is based on the surprising discovery that as few as one episode of blast exposure increases the risk of CTE. Blast exposure is associated with chronic traumatic encephalopathy, impaired neuronal function, and persistent cognitive deficits in blast-exposed military veterans and experimental animals. Early diagnosis and assessment of risk permits physicians to prescribe treatment to reduce or slow progression of impairment before the onset of overt symptoms that become apparent decades after an initial insult or trauma to brain tissue. The invention provides methods and compositions for diagnosis and prognosis of individuals at risk of long term complications related to blast injury or concussive injury.