BDNF and schizophrenia: Importantly, Nrg1 can interact with BDNF in regulating neuronal processes (Mei and Xiong, 2008; Balu and Coyle, 2011), BDNF down-regulation has been reported in schizophrenia (Weickert et al., 2003; Favalli et al., 2012), and BDNF expression changes impact on the sensitivity to social defeat stress (Berton et al., 2006; Krishnan et al., 2007).