Peculiar word use as a possible trait marker in schizophrenia.

Peculiar word use in schizophrenia has been emphasized by many authors, however the definition or the linguistic and clinical correlates of this phenomenon are not clear. We propose a new, standard and reliable method to extract a numerical measure of peculiar word use with operationalized definitions. We applied a modified version of the Controlled Word Association Test (Turkish version) to a pool of healthy subjects (N=55) and used the data as norm to compare the degree of peculiarity and patterns of word association among patients with schizophrenia (N=33), their healthy siblings (N=31) and healthy controls (N=32). We also explored the relationship of peculiar word use with patterns of word association (semantic versus phonologic) and formal thought disorder. Patients and their siblings performed worse on measures of verbal fluency. They also generated more peculiar words and relied less on semantic associations, compared to healthy controls. Peculiar word use was associated with the severity of formal thought disorder and the tendency to make use of phonologic associations in the patient group and their siblings, whereas neither of the word association patterns predicted peculiar word use in the control group. Our results provide empirical support to previous observations about the peculiarity of schizophrenic speech. Peculiar word use could be associated with a deficit to employ semantic classifications in verbal fluency tasks and thus relying more on sound-based associations. Excess use of phonologic associations may be playing a mediating role between semantic processing abnormalities and formal thought disorder.