SUBCLINICAL THOUGHT-DISORDER IN FIRST-DEGREE RELATIVES OF SCHIZOPHRENIC-PATIENTS - RESULTS FROM A MATCHED-PAIRS STUDY WITH THE THOUGHT-DISORDER INDEX

To assess the frequency and quality of formal thought disorder in schi zophrenic patients and their first-degree relatives, a consecutive ser ies of 36 unmedicated patients, 20 siblings of these patients and 37 n ormal control subjects were examined with Holzman's Thought Disorder I ndex (TDI), As a proof of the internal validity of this tool, the pati ents demonstrated significantly more thought disorder than the control s as measured by the TDI total score and various subscores, which prov ed the internal validity of this tool in a German-speaking sample. In addition, in a pairwise comparison with controls who were individually matched by age and sex the patients' siblings had a significantly hig her total TDI score and nonsignificant elevations on several subscores (combinatory and flippant). As to the level of severity of the though t disorder, the siblings mostly took an intermediate position between patients and controls. In conjunction with previous reports from other authors, our findings lend further support to the notion of subclinic al thought disorder as an indicator of familial vulnerability to schiz ophrenia.