The committee concluded that there is sufficient evidence of an association between TBI and depression and aggressive behaviors. The association between mild TBI and posttraumatic stress disorder appears to be different between military and civilian populations. Studies of military personnel who served in the Gulf War led the committee to conclude that there is limited but suggestive evidence of an association between TBI and PTSD. In contrast, studies of civilian populations led the committee to conclude that there is inadequate and insufficient evidence to determine whether an association between TBI and PTSD exists. The studies yielded sufficient evidence of an association between TBI and aggressive behaviors, but limited but suggestive evidence of an association between TBI and decreased alcohol and drug use. Finally, the studies yielded limited but suggestive evidence of an association between moderate to severe TBI and psychoses generally appearing in the second and third years after TBI.
Social functioning is often severely hampered after TBI. Social function in those hospitalized with TBI is adversely affected, relative to those with no injury, for at least 1 year. Results of some studies suggest that difficulties might continue up to 15 years after injury, depending on TBI severity. TBI decreases the probability of postinjury employment in people who were employed before they were injured, lengthens the time it takes them to return to work (if they do return), and decreases the likelihood that they will return to the same positions. Those adverse effects are related to the severity of injury as measured with neurologic severity indicators and are related even more strongly to post-TBI neuropsychologic impairment. Penetrating head injury sustained in wartime clearly is associated with unemployment. The probability of being employed 15 years after the Vietnam War was related to the number of residual neurologic deficits, brain-volume loss, and cognitive status. TBI also adversely affects leisure and recreation, social relationships, functional status, quality of life, and independent living. By 1 year after injury, psychosocial problems appear to be greater than problems in basic activities of daily living. The committee concluded that there was sufficient evidence of an association between penetrating TBI and long-term unemployment and between moderate to severe TBI and long-term adverse social-function outcomes, particularly unemployment and diminished social relationships. However, the committee concluded that there was inadequate and insufficient evidence of an association between mild TBI and long-term adverse social functioning, including unemployment, diminished social relationships, and decrease in the ability to live independently.
There is sufficient evidence of a causal relationship between injury and premature death in people who survive penetrating head injury. There is inadequate and insufficient evidence to determine whether an association exists between mild, moderate, and severe TBI and premature death in people who survive TBI for 6 months or longer; that is largely because of the paucity of studies. Finally, in the subset of patients with moderate or severe TBI either admitted into or discharged from rehabilitation centers or those receiving disability support, there is sufficient evidence of an association between TBI and premature death; however, this finding is limited to patients who have sustained injuries severe enough to warrant inpatient rehabilitation or disability support.
Large population-based registry studies of brain cancer found no association between TBI and brain tumors. However, there is evidence from some other studies of a weak but significant association between TBI and meningioma and of an increase in risk of brain tumors 10 years or more after TBI; this suggests a long latent period before clinical presentation. The committee believes that the possibility of an association between TBI and brain tumors is not a