BDNF and major depressive disorder: Though numerous bibliometric studies have focused on BDNF in neurological and neuropsychiatric disorders such as depression [17], schizophrenia [19], Alzheimer's disease [20], genetic BDNF Val66Met polymorphism [21], and cognitive aging [22], there is currently a noticeable gap in the literature regarding a bibliometric analysis of BDNF's role in chronic pain.