Meanwhile, previous studies revealed that GRIK2 gene knockout mice were more active in several experiments and also had more aggressive displays compared with wild‐type mice (Shaltiel et al., 2008). The contradiction between this study and the previous studies likely results from the racial differences. On the one hand, bipolar disorder is a heterogeneous disease with different classifications and clinical manifestations. The gene discussed is GRIK2; the disease is bipolar disorder.