Genome‐wide association analysis of age at onset in schizophrenia in a European‐American sample

We performed a genome‐wide association analysis to identify genetic variants influencing age at onset (AAO) and examine gene × gender interactions for AAO in schizophrenia (SCZ) using a European‐American sample (1,162 cases). Linear regression model in PLINK was used to test for associations with AAO while the GxE option was chosen to test for the influence of gene × gender interactions. The most significant association with AAO was observed with SNP rs7819815 ( P  = 3.10 × 10 −7 ) at 8q24.22. The next best signal was at 4q25 in COL25A1 gene (rs17039583, P  = 4.30 × 10 −6 ) and the third region was at 4p16.1 (rs17407555, P  = 4.56 × 10 −6 , near RAF1P1 , and rs4697924, P  = 1.23 × 10 −5 within WDR1 gene). Conditional analysis on chromosome 4 indicated that 4p16.1 and 4q25 loci were independent. Furthermore, 2 SNPs (rs16834822 and rs16834824) at 1q43 in RYR2 showed strong associations in the female sample ( P  = 2.10 × 10 −6 and 2.33 × 10 −6 , respectively) and strong gene × gender interactions in influencing AAO ( P  = 9.23 × 10 −7 and 1.15 × 10 −6 , respectively) while the second best region showing gene × gender interaction was at 7q22.3 (rs179863, P  = 2.33 × 10 −6 ). Using an independent sample of 1,068 cases, we could not replicate the associations for above top SNPs; however, we found nominal significance associations for their flanking SNPs ( P  < 0.05). These findings provide evidence of several genetic variants influencing AAO of SCZ. © 2011 Wiley‐Liss, Inc.