SORCS2 and attention deficit-hyperactivity disorder: Regarding the tissue specificity of DNA methylation, although we tried to validate our results using a web tool that can investigate the correlation between methylation of brain, blood, saliva, and buccal cells collected from the same living human (Braun et al., 2019), another way to overcome the issue of tissue specificity is to directly examine the association between the methylation profile of SorCS2 and the precentral or posterior orbital gyri in the postmortem brains of children with ADHD.