Neurocognitive underpinnings of language disorder: Contrasting schizophrenia and mood disorders

Abstract

Language disorder is a deleterious, but poorly understood, symptom of schizophrenia. Burgeoning research suggests that it also occurs in depression and bipolar disorders. Building on prior research, the present study evaluated the degree to which language disorder was associated with neurocognitive deficits in a sample of patients with schizophrenia and mood disorders. Employed in this study were a standard neurocognitive battery and a behavior-based analysis of language disorder from natural speech. Speech samples were collected from two separate counterbalanced conditions administered a week apart. During an “activity” speech condition, participants discussed their daily activities, hobbies and interests. During a “social” speech condition, participants discussed social relationships from their lives. The schizophrenia and mood disorder groups were similar in severity of language disorder during the activity condition. However, there was a significant difference in the severity of language disorder within the schizophrenia patient group but not the mood disorder group. For patients with schizophrenia, language disorder was associated with a range of neurocognitive deficits for both the activity and social speech conditions. For patients with mood disorders, language disorder was significantly associated with poorer neurocognitive functioning during the activity condition, conversely it was significantly associated with better neurocognitive functioning during the social condition. These findings highlight the importance of neurocognition for understanding language disorder across a wide swath of severe mental illnesses. They also emphasize how mitigating factors that exacerbate language disorder may differ in patients with schizophrenia versus mood disorders. Directions for future research are discussed.