To test our hypothesis that neonatal pain would interact with COMT Val158Met genotype to affect SLC6A4 methylation (PC1), a GZLM model was built, in the very preterm group only, with neonatal pain (cumulative skin breaking procedures from birth to term equivalent age) and COMT Val158Met genotypes (Val/Val, Val/Met, Met/Met), and clinical confounders related to prematurity (GA, number of days on mechanical ventilation, SNAP-II day 1, number of surgeries, presence of culture proven infection, cumulative dose of morphine) as covariates. Here, COMT is linked to infection.