Second, we investigated the potential influence of genetic variation on DNA methylation and CU (33, 34). We selected 4 SNPs (rs2301261, rs237915, rs4564970, and rs4686302) that were (a) available in ALSPAC via GWAS (for details see 35), (ii) located within the CpG island examined in the present study, and (iii) have been examined in previous studies in relation to phenotypes relevant to CU (36–39). None of these SNPs were found to associate with DNA methylation levels, CU or the INT−/INT+ groups (full details provided in SI9–10).
