GRIN2A and attention deficit-hyperactivity disorder: Although, these GRIN2A and GRIN2B genes are also susceptible to early onset of schizophrenia function as well as to attentional impairment in ADHD (attention-deficit/hyperactivity disorder) and HD (Arning et al., 2007; Kim et al., 2020; Poltavskaya et al., 2021).