SORCS2 and obesity due to melanocortin 4 receptor deficiency: Although recent human genome-wide association studies have suggested that a gene set related to dopamine signaling is involved not only in ADHD alone but also in the comorbidity of ADHD with obesity and narcolepsy (Mota et al., 2020; Takahashi et al., 2020); in animal studies, lack of SorCS2 reportedly induces ADHD-like behavior by altering the novelty response to psychostimulants and altering the dopaminergic firing pattern of the ventral tegmental area (Olsen et al., 2021).