BDNF and schizophrenia: Sex-specific associations of the BDNF Val66Met polymorphism with cortisol responses to mental stress (Jiang et al., 2017), neurocognitive function in schizophrenia (Kim et al., 2016), sympathetic tone (Chang et al., 2014), HPA axis reactivity to psychological stress (Shalev et al., 2009), and attention-deficit/hyperactivity disorder (ADHD) (Cho et al., 2010) have also been reported.