ATTENTIONAL ABILITIES AND MEASURES OF SCHIZOTYPY - THEIR VARIATION AND COVARIATION IN SCHIZOPHRENIC-PATIENTS, THEIR SIBLINGS, AND NORMAL CONTROL SUBJECTS

Thirty-five schizophrenic patients in the early stages of illness, 26 of their healthy siblings, and 35 normal control subjects performed th e Continuous Performance Test, Identical Pairs version (CPT-IP). Both schizophrenic patients and their siblings were significantly impaired in their attentional performance compared with normal subjects. These results support impaired attention as a vulnerability marker of schizo phrenia and indicate that at-risk siblings of schizophrenic patients d isplay attentional deficits comparable to those found for the offsprin g of schizophrenic parents. By contrast, a decline in performance with the onset of a distraction condition (auditory and visual stimuli) wa s seen only in schizophrenic patients; siblings and normal control sub jects did not differ from one another in response to experimental dist raction. Therefore, it was concluded that differential distractibility is likely to be a state marker of schizophrenia. In clinical assessme nts, healthy siblings rated themselves as experiencing significantly m ore physical anhedonia than did normal control subjects, but the sibli ngs did not differ from normal control subjects in self-rated perceptu al aberrations. Contrary to expectation, performance an the CPT-IP did not correlate significantly with either anhedonia or perceptual aberr ation in high-risk siblings. These results suggest that psychometrical ly measured ''psychosis proneness'' and neuropsychologically detected deficits may tap two nonoverlapping sources of vulnerability to schizo phrenia.