For example, the function of serotonin acting at MT2/5-HT2C receptor heteromers (Kamal et al., 2015) will be perturbed in Mtnr1b KO mice, and of course 5-HT2C receptors have a well-characterised role in anxiety and sociability (Heisler et al., 2007; Millan, 2005), and also in restraining impulsivity (Fletcher et al., 2013; Robinson et al., 2008). This evidence concerns the gene MTNR1B and Anxiety.