Previous studies identified that abnormalities in brain-derived neurotrophic factor (BDNF) levels, elevated endocrine markers such as cortisol, thyroid-stimulating hormone (TSH), and prolactin, as well as structural brain changes observed through neuroimaging—including reduced hippocampal volume and cortical thinning—are consistently associated with major depressive disorder (MDD). Here, PRL is linked to major depressive disorder.