Familial Correlation in Skin Flush Response to Niacin Patch between Schizophrenic Patients and Their First-Degree Relatives

Abstract

Introduction: A reduced flush response to niacin has been found in schizophrenic patients and hence is postulated as a potential indicator for vulnerability to schizophrenia. However, the administration of the test varies in concentrations and time lag for rating. Little is known whether the niacin response has familial aggregation in family members of schizophrenic patients. We aimed to examine the familial correlation in niacin flush response between schizophrenic patients and their first- degree relatives for a variety of concentrations and time lag. Methods: We conducted the niacin test in 153 schizophrenic probands, 217 parents, and 70 siblings. Three concentrations (0.001 M, 0.01 M, and 0.1 M) of niacin were applied to the forearm skin for 5 minutes, and the flush response was rated at 5, 10, and 15 minutes, respectively. On the basis of wider between-individual variation, we chose three ratings for the subsequent analyses of correlation: 0.01M at 5 min and 10 min as well as 0.1 M at 5 min. Results: The Spearman rank correlations in flush response to niacin patch between schizophrenic probands and their first-degree relatives were all significant, ranging from 0.23 to 0.28. Furthermore, the pattern of the correlations remained similar in the ordinal logistic regression analysis of relatives' response on probands' response with adjustment for potential confounders, including age, sex, allergy, tobacco smoking, and coffee drinking. Conclusions: These findings provide further support for the potential of niacin flush response as a vulnerability indicator to schizophrenia.