The cost of TBI is enormous from a public-health perspective and likely to be underestimated. There is a high financial cost, determined by a host of acute and chronic injuries in the context of broad and extended personal disability, and the fact that TBI often occurs to soldiers in the course of their duties in war makes this an issue of even greater national concern. The psychiatric aspects of TBI that are most often identified and studied are the related risks of depressive and anxiety disorders, as discussed see above, and well-controlled outcome studies are available from which conclusions regarding associations can be drawn.
TBI has been implicated in other personality and behavioral outcomes, but on the basis of fewer studies, which are likely to have been conducted with less methodological rigor. The other outcomes include aggression, irritability, emotional reactivity, sleep disorders, sexual dysfunction, reduction in insight, and personality disorders, all converging on poor psychosocial function. Complicating the interpretation of the studies is the fact that many studies have been poorly controlled, may have been biased, and may have overlooked premorbid factors in the behavioral outcomes. The committee reviewed the literature in this area and found primary studies whose methods were scientific and whose outcomes can be accepted with confidence; these studies are supplemented by secondary studies of suitable rigor that are not definitive.
Two primary studies found that TBI is associated with subsequent aggressive behavior, but one primary study found no effect of TBI on criminal conviction. A primary study by Ommaya et al. (1996) examined the relationship between aggressive personality traits in TBI. They used military populations and identified “adverse personnel action” and “discharge from military service” as two overall markers of poor outcome in an attempt to understand the relationship between premorbid behavior, TBI, and postinjury behavior. The study cohorts consisted of 1,617 active-duty Army personnel who were hospitalized in FY 1992 and FY 1993 for head injuries caused by fighting or for other trauma; the comparison group was all 4,626 active-duty Army personnel who were hospitalized for orthopedic injuries caused by fighting or other means; a “normal” active-duty population of 9,997 (without injury) was a second reference group. The outcomes were “military service discharge” (administrative-behavioral, administrative-criminal, or medical) and other “adverse personnel action.” Several variables were found to be important confounding factors for behavioral discharge and criminal conviction—age, marital status, educational level, pay grade, time in pay grade, and years of active service—and were controlled for in the analyses. Individuals who sustained TBI had a worse behavioral outcome than those who had orthopedic injury, in “adverse action” and “discharge for behavioral criteria or criminal conviction,” whereas TBI did not affect “medical discharge.” Specifically, the percentage of individuals encountering “adverse action” was 21% in the TBI group (overall) and 13% in the orthopedic-injury group (overall); the percentage encountering “discharge for behavioral disturbance or criminal conviction” was 11% and 6%, respectively; and the percentage encountering “medical discharge” was 9% and 11%,