There have since been numerous reports examining the role of BDNF in psychiatric disorders and it could emerge as a valuable biomarker in depression and treatment response (Polyakova et al., 2015) The neurobiology of BDNF and its role in antidepressant actions and psychiatric disorders are discussed in detail in two recent reviews (Castren and Monteggia, 2021; Wang et al., 2022). Here, BDNF is linked to major depressive disorder.