No association of single nucleotide polymorphisms in the micro-opioid receptor subunit gene with idiopathic generalized epilepsy.

We have investigated the reported association (p = 0.019) between the A118G single nucleotide polymorphism (SNP) of the opioid receptor micro subunit gene (OPRM1) and idiopathic absence epilepsy (IAE). Five SNPs, including A118G, were investigated by association studies in a sample of 240 probands with idiopathic generalized epilepsy (IGE), including 110 with IAE, and 257 controls. No significant association was found for A118G with IGE or IAE. The difference between the two studies was in the control samples that had significantly different allele frequencies (p = 0.00005), suggesting that population stratification may explain the earlier significant association with IAE. In the current study, none of the other four SNPs was significantly associated with IGE or IAE. Our results provide no support for association of A118G with either IAE or IGE and also exclude association in our sample of a small-to-moderate gene effect with IGE from a large part of OPRM1.