Speech Anomalies as a Symptom of Formal Thought Disorder in Schizophrenia: The Sensitivity of The Thought and Language Dysfunction Scale on Speech Related Items
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Formal thought disorder (FTD) is a core symptom of schizophrenia and has been described as a set of language, thinking and communication deficits. The diagnosis of FTD takes place using a clinical rating scale that often encompasses speech related items. However, the relation between FTD and speech anomalies has yet to be explored. This study therefore investigated whether the speech related items of the Thought and Language Dysfunction Scale (TALD) corresponded with automatically measured features of the acoustic speech signal. Spontaneous speech of patients with schizophrenia (n=42) as well as healthy controls (n=42) was analysed using acoustic speech analysis software programs for 11 speech parameters. Results showed that, in comparison to healthy controls, patients with schizophrenia spoke softer, had a higher F1 frequency, made longer pauses, varied less in speech volume, had more shimmer, spoke a smaller percentage of the time and had a slower speech rate. However, no significant differences were found between patients with severe FTD and patients with less severe FTD. The sensitivity of the TALD was assessed by analysing the correlation between five speech related items on the scale and their associated speech parameters. Only two out of five items of the TALD correlated significantly with their associated speech parameter, suggesting the TALD is an inaccurate clinical tool with regards to speech related anomalies.