Verbal fluency, clustering, and switching in patients with psychosis following traumatic brain injury (PFTBI)

Verbal fluency in patients with psychosis following traumatic brain injury (PFTBI) has been reported as comparable to healthy participants. This finding is counterintuitive given the prominent fluency impairments demonstrated post-traumatic brain injury (TBI) and in psychotic disorders, e.g. schizophrenia. We investigated phonemic (executive) fluency (3 letters: 'F' 'A' and 'S'), and semantic fluency (1 category: fruits and/or vegetables) in four matched groups; PFTBI (N=10), TBI (N=10), schizophrenia (N=23), and healthy controls (N=23). Words produced (minus perseverations and errors), and clustering and switching scores were compared for the two fluency types across the groups. The results confirmed that PFTBI patients do show impaired fluency, aligned with existing evidence in TBI and schizophrenia. PFTBI patients produced the least amount of words on the phonemic fluency ('A') trial and total score, and demonstrated reduced switching on both phonemic and semantic tasks. No significant differences in clustering performance were found. Importantly, the pattern of results suggested that PFTBI patients share deficits with their brain-injured (primarily executive), and psychotic (executive and semantic), counterparts, and that these are exacerbated by their dual-diagnosis. These findings add to a very limited literature by providing novel evidence of the nature of fluency impairments in dually-diagnosed PFTBI.