SORCS2 and attention deficit-hyperactivity disorder: We suggested that SorCS2 methylation is involved in ADHD through methylation array analysis of MZ twin discordant cases and case-control groups, while previous epigenome-wide studies found no evidence that SorCS2 methylation is involved in either children or adults with ADHD (van Dongen et al., 2019; Neumann et al., 2020; Rovira et al., 2020).