Language in schizophrenia and aphasia: the relationship with non-verbal cognition and thought disorder

<b>Objective:</b> To determine the relationship between language abnormalities and broader cognitive impairment and thought disorder by examining language and cognition in schizophrenia and aphasia (a primary language disorder). <b>Methods:</b> Cognitive and linguistic profiles were measured with a battery of standardised tests, and compared in a clinical population of <i>n</i> = 50 (<i>n</i> = 30 with schizophrenia and <i>n</i> = 20 with aphasia) and <i>n</i> = 61 non-clinical comparisons (<i>n</i> = 45 healthy controls and <i>n</i> = 16 non-affected first-degree relatives of patients with schizophrenia). <b>Results:</b> Both clinical groups showed linguistic deficits. Verbal impairment was more severe in participants with aphasia, whereas non-verbal performance was more affected in participants with schizophrenia. In schizophrenia, but not in aphasia, verbal and non-verbal performance were associated. Formal thought disorder was associated with impairment in executive function and in grammatical, but not naming, tasks. <b>Conclusion:</b> While patients with schizophrenia and aphasia showed language impairments, the nature and cognitive basis of these impairments may be different; language performance disassociates from broader cognitive functioning in aphasia but may be an intrinsic expression of a broader cognitive impairment in schizophrenia. Thought disorder may represent a core malfunction of grammatical processing. Results suggests that communicative ability may be a valid target in cognitive remediation strategies in schizophrenia.