The possibility that the abnormal behaviours of NK1R-/- mice echo those seen in ADHD patients is supported by an association between polymorphisms in, or near, the TACR1 receptor gene (the human equivalent of the Nk1r gene) and increased vulnerability to ADHD (Sharp et al.2014; Yan et al.2010). Here, TACR1 is linked to attention deficit-hyperactivity disorder.