Figurative language production in schizophrenia, bipolar disorder, and depression

Mental disorders, such as major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ), are often associated with alterations in speech and language production and/or processing. In particular, the processing of figurative language has been found to be impaired, with expressions being interpreted in a concretistic way. These findings are often based on figurative language comprehension tests and other types of behavioral tasks. In contrast, the production of figurative expressions is understudied, especially in MDD and BD.

N = 157 participants (n = 49 MDD, n = 19 BD, n = 19 SZ, and n = 70 healthy controls (HC)) provided speech samples based on a picture description task. 1900 min of spoken language were transcribed, and instances of metaphors as well as idioms were annotated. Group comparisons in the frequency and source domain diversity of figurative language and associations between figurative language use, psychopathology, and cognitive performance were investigated using ANCOVA, correlational, and regression analyses, corrected for age, sex, years of education, and medication.

Patients exhibited a proportionally higher use of figurative language compared to HC. No significant differences emerged in figurative language production across diagnostic subgroups. Additionally, neither psychopathology nor cognitive performance showed a significant correlation with figurative language use, either in the overall sample or within individual diagnostic groups. High inter-individual variability in figurative language production was observed.

This study compared figurative language production across HC, MDD, BD, and SZ. During a picture description task, patients produced a higher proportion of idioms and metaphors than HC. Overall, this study contributes to the growing body of knowledge on figurative language use across diagnoses.