CI, 1.06–3.00) when the analysis was restricted to those who had no prior history of depression. Three other secondary studies also found that depression was associated with TBI (Masson et al., 1996; Hibbard et al., 1998, Deb et al., 1999). In contrast, Malec et al. (2007) examined 51 patients who had moderate to severe TBI, 42 patients who had mild TBI, and 42 controls who had orthopedic injuries and found no difference in depression rates among the three groups.

The committee reviewed four primary and five secondary studies of mood disorders—major depression—and findings were consistent. The preponderance of studies found that groups with TBI (mild, moderate, or severe) had higher rates of major depression 6 months or longer after TBI than did appropriate comparison groups (including non-TBI injured controls). Three studies (Fann et al., 2004; Jorge et al., 2004; Vanderploeg et al., 2007) provided some control for differences in depression before TBI; all three provided data suggesting that the observed association between TBI and major depression could not be explained by prior depression. Nevertheless, it should be noted that the available data suggest that prior mood disorder may predispose to TBI (Fann et al., 2002; Vassallo et al., 2007) and that post-TBI major depression is more frequent in people who had major depression before TBI than in people who did not (Fann et al., 2004).

In contrast to depression, there are few studies on the relationship between mania or bipolar disorder and TBI (Koponen et al., 2002; Sagduyu, 2002; Silver et al., 2001). Koponen et al. (2002) and Silver et al. (2001) reported a prevalence rate of 1.7% and 1.6%, respectively, of TBI patients who met criteria for bipolar disorder. They concluded that the prevalence did not differ significantly from that found in control populations. Sagduyu (2002) examined 535 patients who had bipolar disorder. Of the 126 patients who reported a history of mild TBI, 72 reported symptoms of bipolar disorder prior before the injury, and 54 reported symptoms after the injury. Those studies do not provide consistent or compelling evidence regarding an association between TBI and mania or bipolar disorder.