Supplementary Material for: Association between Neuropeptide Y Gene Polymorphisms and Alcohol Dependence: A Case-Control Study in Two Independent Populations

<b><i>Background:</i></b> Alcohol dependence is a chronic, progressive neurobiological brain disorder. Previous research reported an inverse association between ethanol drinking and cerebral neuropeptide Y (NPY) levels. There are conflicting results of studies on <i>NPY</i> gene polymorphisms in association with alcohol dependence in humans. <b><i>Methods:</i></b> To assess the role of the <i>NPY</i> gene in alcohol dependence, we genotyped three polymorphisms - in a sample of 195 subjects from the Kota population (80 alcohol dependence and 115 controls) and 141 subjects from the Badaga population (80 alcohol dependence and 61 controls). Phenotype was defined based on the DSM-IV criteria. Genotyping was performed using sequencing. Association of the <i>NPY</i> gene with alcohol dependence was tested by using logistic regression and haplotype analyses and linkage disequilibrium. <b><i>Results:</i></b> All three polymorphisms were found to be in the Hardy-Weinberg equilibrium in both populations. The results of our study reveal a significant association between G1258A and alcohol dependence in both the Kota and Badaga populations. The linkage disequilibrium between the markers is not strong or significant. Haplotype analysis also did not show significant association between the <i>NPY</i> gene and alcohol dependence. <b><i>Conclusion:</i></b> These data support the hypothesis that alcohol dependence is influenced by the NPY G1258A polymorphism in Indian populations.