with 9 (20.5%) of the 44 TBI patients without major depression (p < 0.001). Of the 23 patients with both major depression and an anxiety disorder, 14 had generalized anxiety features, 2 had generalized anxiety and panic attacks, and 7 met the criteria for PTSD. Significant aggressive behavior was seen in 17 (56.7%) of the 30 patients with TBI and major depression compared with 10 (22.7%) of the 44 TBI controls (p = 0.003). Half the 30 patients with TBI and major depression received the diagnosis at their initial evaluation, and an additional 9 patients received the diagnosis at the 3-month follow-up. There were no significant differences between TBI patients with and without major depression in demographic variables or the use of alcohol or other drugs. Those with TBI and major depression had a significantly higher frequency of a personal history of mood disorders (p = 0.01) and anxiety disorders (p = 0.05).

A recent study by Hoge et al. (2008) examined consequences of mild TBI in US soldiers that saw a high level of combat during a year-long deployment in Iraq. About 3–4 months after return from Iraq, soldiers were sent a questionnaire covering injury, combat intensity, physical symptoms, major depression, and PTSD. Soldiers were considered to have mild TBI if they answered yes to any of three questions—about losing consciousness, being dazed or confused, or not recalling the injury. The answers to those questions were used to form two subgroups within the mild-TBI group to determine whether LOC was a stronger predictor (that is, one that had LOC and one that had dazing or confusion or did not recall the injury—the second made up the altered-mental-status group). The final samples were 124 with mild TBI and LOC, 260 with mild TBI and altered mental status, 435 with other injury, and 1,706 with no injury. PTSD was present in 43.9% with LOC, in 27.3% with altered mental status, in 16.2% with other injury, and 9.1% without injury (p < 0.001). Major depression was associated with LOC more than with other injury (22.9% vs 6.6%, p < 0.001) but was not associated with altered mental status more than with other injury (8.4% vs 6.6%, p = 0.39). Limitations of this study included a failure to control analyses for major depression before TBI. Furthermore, groups were not well matched for combat intensity. Finally, it is unclear how one could effectively distinguish between a history of LOC or altered mental status attributable to TBI and similar phenomena attributable to dissociation4 in the face of emotional trauma.

Secondary Studies

The committee identified five secondary studies that looked at the association between TBI and mood disorders, specifically, depression. Limitations of these studies include the self-reported diagnosis of TBI and retrospective assessment of mood disorders.

Vanderploeg et al. (2007) conducted a cross-sectional study of the long-term psychiatric, neurologic, and psychosocial outcomes associated with self-reported mild TBI. A subsample of 4,384 veterans was categorized into three groups: no motor-vehicle accident and no TBI (normal control, n = 3,214); injured in a motor-vehicle accident but no TBI (motor-vehicle accident control; n = 539); and TBI with altered consciousness (mild-TBI group; n = 254). Results indicate that the mild-TBI group had a higher frequency of depression than the normal control group (OR, 1.77, 95% CI, 1.13–2.78). The mild-TBI group also had a higher frequency of prior depression than the normal control group, but the adjusted OR was virtually identical (1.78; 95%


Dissociation is a mental state in which a person’s thoughts, emotions, or memories are compartmentalized, usually in response to a traumatic event. Some dissociative disorders include psychogenic amnesia, psychogenic fugue, and multiple personality.

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement