GRM7 and attention deficit-hyperactivity disorder: The relationship between ELFN1 and ADHD is also supported by the genetic association of GRM7 (mGluR7) with ADHD, which has been observed in some cohorts (Elia et al., 2012; Park et al., 2013; Akutagava-Martins et al., 2014; Zhang et al., 2021) and with treatment response to methylphenidate among ADHD patients (Mick et al., 2008; Park et al., 2014).