BDNF and major depressive disorder: The reduction of neurotrophins in the hippocampus and PFC was one of the major pathological features in anxiety and depression (Thoenen 1995, Autry & Monteggia 2012, Kristiansen & Ham 2014, Notaras et al. 2015, Ayanlaja et al. 2018, Koo et al. 2019).