Spoken language biomarkers in Turkish-speaking schizophrenia patients: Evidence from linguistic analysis and word...

Schizophrenia (SZ) disrupts language in ways that may be universal across languages. This study investigated whether linguistic anomalies previously observed in SZ also occur in Turkish, a morphologically rich and agglutinative language. We hypothesised that SZ patients would differ from healthy controls (HCs) across multiple linguistic domains, including features typically sensitive to cross-linguistic variation.

Speech characteristics of 50 native Turkish-speaking SZ patients were compared with 50 HCs matched for age, sex, length of education, and handedness. Speech data were collected in 15-minute interviews. The interview recordings were transcribed and analysed for various lexical, syntactic, and phonological measures using CLAN, and compared for discourse measures using fastText word embedding models.

The number of words produced per minute, mean length of utterance, average word frequency, the number of filled pauses, discourse coherence, and question-response similarity were lower in the patient group than in the control group. The content word-function word ratio, sentence prediction loss, type-token ratio, number of silent pauses, and silent pauses-to-total speech ratio were higher in the patient group than in the control group. Specific clinical and sociodemographic variables were identified as predictors of speech abnormalities in patients.

The hypothesis was confirmed. Turkish-speaking SZ patients displayed speech patterns similar to those reported in other language groups, including language-sensitive variables. This supports the idea of universal linguistic disruptions in SZ. The findings are particularly valuable given the scarcity of research on Turkish, a low-resource and typologically distinct language.