Case–control comparative analysis on LD, performed between the genetic variants located on the same chromosome, revealed strong LD between GRM5 rs905646-rs11020772 (Fig. 1B; D′ = 0.87, r2 = 0.68) in the ADHD probands and the male probands (Fig. 1D; D′ = 0.90, r2 = 0.71) as well as in all controls (Fig. 1A; D′ = 0.80, r2 = 0.62) and male controls (Fig. 1C; D′ = 0.85, r2 = 0.71) respectively. Here, GRM5 is linked to attention deficit-hyperactivity disorder.