Familial association of schizophrenia symptoms retrospectively measured on a lifetime basis

Objective: The objective of this study was to characterize the familial associations of symptoms or symptom dimensions of schizophrenia, as a component of the effort to delineate suitable phenotypic markers under the homogenous genetic control. Methods: Clinical symptoms of the patients were evaluated on a lifetime basis, with the Korean version of the Diagnostic Interview for Genetic Studies and the Krawieka scale. Our sample consisted of 54 sibling pairs who were concordant for Diagnostic and statistical manual of mental disorder-IV schizophrenia or schizoaffective disorder. Results: At the individual symptom level measured by the Diagnostic Interview for Genetic Studies, we observed a statistically significant degree of concordance within the sibling pairs for auditory hallucination (kappa=0.600, chi(2)=15.193, P=0.000). The within-sibling resemblance of this symptom was also indicated by the results of correlation analyses of individual items of the Krawiecka scale (partial correlation coefficient=0.423, P=0.005). Among the individual symptoms or symptom dimensions of the Krawiecka scale, the 'anxious' (partial correlation coefficient=0.469, P=0.001) and the 'affective dimension' (including the items of 'anxious' and 'depressed') (partial correlation coefficient=0.436, P=0.003) were also determined to indicate significant intra-pair correlations after controlling for potential confounding variables, such as sex, duration of illness, and age of onset. Conclusions: The results of this study suggest that familial factors, possibly genetic factors, contribute a liability to the development of auditory hallucinations. This symptom might then prove useful as a phenotype marker in future genetic studies.