Traumatic brain injury (TBI) is the major cause of death and disability among young adults. In spite of preventive measures, the incidence of a TBI associated with motor vehicle accidents, falls, assault, and high-contact sports continues to be alarmingly high and constitutes a major public health concern. In addition, the recent military operations in Iraq and Afghanistan have resulted in a large number of persons with blast injuries and brain trauma. Taking into account that cognitive and behavioral changes have a decisive influence in the recovery and community reintegration of patients with a TBI, there is a renewed interest in developing systematic studies of the frequency, mechanism, and treatment of the psychopathological alterations observed among these patients.
Each year, an estimated 1.5 million Americans sustain a TBI that requires hospitalization. As a result of these injuries, 80,000 to 90,000 patients experience long-term disability.1 There is consensus that cognitive, emotional, and behavioral problems constitute the major source of disability for TBI patients.
The neuropsychiatric consequences of a TBI can be studied from a dimensional perspective using neuropsychological tests and behavioral scales that have been extensively validated in acute-care settings and rehabilitation services.2-5 Cognitive and behavioral morbidity can also be assessed from a categorical, disease-based perspective, which assumes that psychiatric disorders, although diagnosed through a recognized constellation of symptoms, have an identifiable biological substrate, a distinct clinical prognosis, and an expected treatment response.6
Fann and colleagues7 examined the risk of psychiatric illness after a TBI in an adult health maintenance organization population. They compared the frequency of psychiatric disorders among 939 patients with a TBI and 2817 controls. The prevalence of any psychiatric illness in the first year was 49% following a moderate to severe TBI, 34% following a mild TBI, and 18% in the control group. Among study participants without a history of psychiatric illness, those with moderate to severe TBI were 4 times (95% confidence interval [CI], 2.4 to 6.8) more likely to sustain any psychiatric illness in the 6 months following a TBI than those without a TBI. The risk was 2.8-fold higher (95% CI, 2.1 to 3.7) in patients with a mild TBI compared with study participants who did not have a TBI.7
Mood disorders are the most frequent psychiatric illness observed among patients with a TBI.8-10 Hibbard and colleagues11 used a structured interview and DSM-IV criteria to identify Axis I psychopathology in 100 adults with a TBI who were evaluated, on average, 8 years after trauma. The prevalence of major depression in this population was 61%. More recently, Kreutzer and colleagues12 studied the prevalence of major depressive disorder in a sample of 722 outpatients with a TBI, evaluated an average of 2.5 years following brain injury. Major depression, defined using DSM-IV criteria, was diagnosed in 303 patients (42%). Findings from a prospective study indicate that the frequency of mood disorders was significantly greater in patients with a TBI than in a control group of patients who had had an orthopedic trauma. A mood disorder developed at some time during the first year after injury in 46 of 92 patients with a TBI (51%), compared with 6 of 27 patients (22%) with multiple traumatic injuries but without CNS involvement. In addition, the frequency of major depressive disorder was significantly greater in patients with TBI than in the control group.13 Thus, mood disorders were significantly more frequent in patients with a TBI than in patients with similar background characteristics who underwent similar levels of stress (eg, motor vehicle accidents) but who did not sustain brain injury. This suggests that structural brain damage associated with a TBI constitutes an important contributing factor to the development of affective disorders. Furthermore, patients who experience major depression following a TBI frequently show structural and/or functional alterations in the prefrontal cortex as evidenced by abnormal performance on neuropsychological tests or by abnormal neuroimaging findings.13-15
Emotional processing and mood regulation involves the complex interaction between prefrontal regions (eg, anterior cingulate gyrus, orbitofrontal cortex) and limbic structures (eg, amygdala, hippocampus, ventral striatum). Different forms of traumatic lesions such as diffuse axonal injury and cerebral contusions may result in disruption of these neural circuits and, consequently, in affective disturbance. Furthermore, these changes may persist and evolve with time.
A significant proportion of patients in whom mood disorders develop following a TBI will progress to a more chronic and recurrent form of these psychiatric conditions, spanning many years. Thus, the prevalence of psychiatric disorders continues to be significantly higher in TBI patients than in control groups many years after the traumatic injury.16-18
A recent community study suggests an association between a history of a TBI and an increased lifetime prevalence of major depression.17 The investigators found that the lifetime prevalence of major depression among men who had sustained a TBI during the Second World War was 18.5% versus 13.4% for a comparable group without a TBI. Koponen and colleagues18 assessed the frequency of Axis I and Axis II disorders in a group of 60 patients 30 years after sustaining a TBI. The patients showed a lifetime prevalence of major depression of 26.7%. Overall, these findings suggest that patients with a TBI have recurrent depressive disorder throughout their lifetime at a significantly higher frequency than comparable patients without a TBI. When present, affective disturbances have a large impact on family relationships, social integration, and return to productive activity.
Anxiety disorders occur in a significant proportion of patients with a TBI and frequently coexist with depressive disorders (Table 1).18,19 There is a significant degree of comorbidity between mood and anxiety disorders among patients with a TBI. For example, about two-thirds of patients in whom major depression develops also meet diagnostic criteria for generalized anxiety disorder.13
Posttraumatic stress disorder (PTSD) is another frequent psychiatric complication in patients with traumatic injuries.20 Whether unconsciousness and posttraumatic amnesia associated with a TBI would preclude the onset of PTSD in patients who have had a life-threatening experience, such as a motor vehicle accident or physical assault, has been widely debated. In fact, PTSD has been described in patients with a TBI of different degrees of severity, even among those patients who have partial or fragmentary recollection of the contingencies of the traumatic episode.21-23 Recently, Glaesser and colleagues24 assessed the occurrence of PTSD in a group of 46 patients with a TBI who were admitted to an acute neurorehabilitation clinic. They concluded that a TBI and PTSD are not mutually exclusive. However, PTSD was unlikely to develop in victims of accidents if trauma had resulted in a prolonged period of unconsciousness. Bryant and colleagues25 analyzed the relationship between resting heart rates at 1 week and 1 month following a severe TBI and a PTSD diagnosis assessed 6 months after the injury. In these trials, PTSD developed in 16 of 68 (23%) severely injured patients. Compared with patients in whom PTSD did not develop, the patients had significantly higher heart rates at 1 week but not at 1 month after trauma. These findings suggest that fear conditioning can occur independently of the level of awareness and contribute to the onset of PTSD. These investigators also reported that patients who had PTSD at 6 months following a severe TBI had significantly poorer functional and vocational outcomes than did patients who did not have PTSD.26