Objectives:This study aims at examining familial associations of symptoms and clinical characteristics in affected sibling or relative pairs of schizophrenia as an effort to identify genetically homogeneous phenotypes.
Methods: Forty-seven relative pairs with DSM-IV diagnosis of schizophrenia from thirty-five Korean families multiply affected with schizophrenia were ascertained. Direct interviews were done using the Korean version of Diagnostic Interview for Genetic Studies (DIGS). The Krawieka Rating Scale and the Schedule for the Deficit Syndrome were also applied for further evaluation of psychopathologies. Intra-familial concordances and correlations of clinical characteristics and symptoms were tested using chi-squared-test and Spearman’s correlation.
Results: Significantly high concordance rate within relative pairs was found for the diagnosis of paranoid vs. non-paranoid subtype (chi-squared=7.623, p=0.006, df=1). Deficit vs. non-deficit syndrome also showed significant concordance (chi-squared=3.850, p= 0.0497, df=1). Among single symptom items in DIGS, only ’auditory hallucination’ showed significant concordance rate (chi-squared= 5.503, p=0.019, df=1). Factor analysis for symptoms items in the Krawiecka Rating Scale indicated three symptom dimensions; negative, psychotic and affective. Psychotic (rho=0.442, p=0.003) and affective dimension scores (rho=0.427, p=0.004) showed significant intra-familial correlations. Age at onset of recognized psychotic symptoms showed significant correlation only within the male sibling pairs.
Conclusion: Familial factors, possibly genetic factor contribute to the phenotypic characteristics of paranoid vs. non-paranoid subtype, deficit vs. non-deficit syndrome, auditory hallucination, and affective syndrome. It supports their use in the delineation of homogeneous subgroups for future genetic studies
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