BDNF and depressive symptom measurement: On the other hand, the increase in BDNF expression in the hippocampus is a typical feature of standard antidepressants (Harmer et al., 2017; Monteggia et al., 2004; Kraus et al., 2017; Björkholm and Monteggia, 2016), while it is widely acknowledged that chronic stress causes a down-regulation of BDNF protein and mRNA in the hippocampus (Zaletel et al., 2017), an effect that is strictly linked with depression (Duman and Monteggia, 2006).