In comparison to studies using animal models, the expression of some common genes in human major depressive disorder, such as Htr2a, Ntrk3, Crhr1, Ntrk2, Crh, complement component 3 and fatty acid binding protein 7 undergoes changes in both short-term and long-term treatments in depression animal models [210]. This evidence concerns the gene NTRK2 and major depressive disorder.