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Traumatic Brain Injury in Adults

See the Traumatic Brain Injury (Adults) Evidence Map for summaries of the available research on this topic.


The scope of this page is limited to traumatic brain injury in adults (ages 18 and older). A Portal page on TBI for younger individuals is in the process of being developed.

Traumatic brain injury (TBI) is a form of nondegenerative acquired brain injury, resulting from an external physical force to the head (e.g., fall) or other mechanisms of displacement of the brain within the skull (e.g., blast injuries). Consistent with the diagnostic criteria detailed in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5; American Psychiatric Association, 2013), TBI is associated with one or more of the following characteristics:

  • changes in levels of consciousness;
  • memory disturbances;
  • confusion associated with deficits in orientation;
  • neurological signs, such as brain injury observable on neuroimaging, new onset or worsening of seizure disorder, visual field deficits, hemiparesis, etc.

TBIs can result in focal damage (e.g., gunshot wound) or be more diffuse in nature (e.g., diffuse axonal injury), and the symptoms can vary depending on the site of lesion and extent of damage to the brain. TBI is often associated with polytrauma (injury to the brain in addition to one or more other body systems). While some symptoms may appear immediately after the injury, others may evolve over time consistent with anatomical changes in the neural substrates following the injury and comorbid conditions, such as post-traumatic stress disorder (PTSD), depression, anxiety, and sleep disturbance (Department of Defense Deployment Health Clinical Center, n.d.).

TBI can be categorized as mild, moderate, or severe based on the extent and nature of injury, duration of loss of consciousness, post-traumatic amnesia, and the severity of confusion at initial assessment during the acute phase of the injury (DSM-5; American Psychiatric Association, 2013). See common classifications of TBI. These categorical labels describe the extent of neurological injury to the brain and are not necessarily reflective of the extent of functional deficits or predictive of the recovery from the injury.

Mild traumatic brain injury (mTBI) is marked by severity of injury that does not exceed loss of consciousness greater than 30 minutes, an initial Glasgow Coma Scale (GCS) of 13-15 after 30 minutes of onset of injury, and memory loss not greater than 24 hours (Ontario Neurotrama Foundation, 2013). mTBI is often associated with concussions, which are characterized by the physical and cognitive sequelae of TBI in the absence of overt neuroimaging findings. mTBI is typically diagnosed by the individual's self-reports of symptoms and retrospective attribution to brain injury.

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