Several markers exhibited gender specific association effects. For instance, markers rs1978340 & rs3791878 (at 5′ near GAD1 gene) showed effects in males only with minor allele as the risk allele (has early AD age-at-onset), while the same markers showed no such effects in females. Females with minor allele had later age-at-onset of AD (Table 3, males and females have coefficients in opposite directions) though not statistically significant. Similarly, marker rs2839673, which is a coding SNP (in exon 6 of GAD2) was modestly associated with withdrawal severity showing opposite direction of coefficients in females and males. Haplotypic analyses results (Table 4) showed similar patterns of bi-direction effects by genders and the associations mainly restricted to one gender. For instance, haplotype 2111 in GAD1 exhibited strong association with initial sensitivity to ethanol and tolerance/maximum drinking only in females, and haplotype 1121 exhibited strong association with withdrawal severity only in males. Because both haplotypes are not common haplotypes (frequency around 1–2%, which represents 13–25 chromosomes in our sample), we did not test for gender interactions directly in the present study. The real contribution
