Does the Schizotypal Personality Questionnaire reflect the biological-genetic vulnerability to schizophrenia?

We investigated whether the Schizotypal Personality Questionnaire (SPQ) [Schizophr. Bull. 17 (1991) 555.] could be an indicator of the biological-genetic vulnerability to schizophrenia. We hypothesized that the mean scores on three dimensions of the SPQ of different groups of relatives of patients with schizophrenia would parallel their risk for developing schizophrenia. The SPQ was administered to 51 first-episode schizophrenia patients, 63 parents of schizophrenia patients, 42 siblings of schizophrenia patients and 12 children of schizophrenia patients. Patients differed from the relatives on all three dimensions. Siblings and children scored significantly higher than parents on Positive Schizotypy, and the insignificant difference between the siblings and children was in the expected direction. The results could not be explained by the differences in age, sex, IQ or substance abuse. No differences were found for Disorganization Schizotypy between the relatives. Children scored higher than parents on Negative Schizotypy. The current study offers support to the hypothesis that the positive dimension of SPQ reflects the genetic vulnerability to schizophrenia.