The individual SNP analysis confirmed an association for the valine/methionine variant with AD-P. Haplotype analyses revealed that the alleles at four loci (rs737865, rs737864, intron 1 C2754delC, rs4680) interacted to create the risk of psychosis in AD, as A-C-C-G haplotype (OR=2.08, 95% CI=1.02-4.27, P=0.044) and G-C-delC-G haplotype (OR=2.54, 95% CI=1.32-4.90, P=0.006) in respect to the most common and not-at-risk A-C-C-A haplotype which was significantly overrepresented in AD-P.