Epigenomic socioeconomic studies more similar than different

In a recent issue of PNAS, Lam et al. (1) identified three CpG sites associated with early-life socioeconomic status (SES) in adult blood DNA. The authors observed that this small number of associated CpG sites “appears to be at odds” with the 1,252 gene promoters found in our study of 40 adult males stratified by early-life SES (2). The authors suggest that our analysis of the data inflated the statistical significance of methylation associations and wonder whether blood composition may have further inflated the results.