Violent blows or jolts to the head can cause traumatic brain injury (TBI), and there are currently about five million people in the U.S. living with some form of chronic impairment after suffering a TBI. Even in a mild form, TBI can lead to lifelong nerve cell deterioration associated with a wide array of neuropsychiatric conditions. Tragically, there are no medicines to protect nerve cells after injury. Behind aging and genetics, TBI is the third leading cause of Alzheimer’s disease (AD), yet the link between these two conditions is not understood.