Executive dysfunction in psychosis following traumatic brain injury

Objective Executive dysfunction is well established in patients with traumatic brain injury, and in schizophrenia. However, assessments of executive function in psychosis following traumatic brain injury (PFTBI) are limited, inconsistent, and often do not reflect the prominent deficits demonstrated in TBI and schizophrenia. This research represents the first systematic and standardized measurement of executive function in a PFTBI cohort, and comparison with healthy and single-diagnosis controls. Method Patients with PFTBI (n =10) were recruited from the Royal Talbot Hospital (Kew, Australia) and matched on demographic, injury, and illness variables with traumatic brain injured patients without psychosis (n =10), schizophrenia patients (n =23), and healthy individuals (n =23). All participants completed identical measures of executive function, including: the Stroop Task (Delis et al., 2001), the Trail Making Test (Reitan, 1958), and the attention subtest of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS; Randolph, 1998). Statistical comparisons were made using univariate Analysis of Variance and Student-Newman-Keuls post hoc tests. Results Significant executive dysfunction was shown by patients with PFTBI on all measures. PFTBI patients further demonstrated the poorest performance relative to all three comparison cohorts. Conclusion These data present novel evidence of substantially impaired executive function in dually-diagnosed PFTBI patients, both relative to healthy controls, and the impairments of their brain-injured, and psychotic, counterparts. We speculate that PFTBI executive deficits are underpinned by exaggerated structural and functional disconnectivity established in both TBI (Lipton et al., 2009; Kurowski et al., 2009) and schizophrenia (Andreasen et al., 1998; Zakzanis et al., 2005), particularly with respect to network connections in the dorsolateral and ventromedial prefrontal cortices