The antidepressant effects of Yulangsan polysaccharide (YLSP) have been demonstrated in animal models of “behavioral despair” (Liang et al., 2010), exerting a suppressive effect on depression through the upregulation of monoamine neurotransmitters, enhancement of prefrontal cortical adenylate cyclase activity, and increased hippocampal expression of BDNF (Liang et al., 2012). Here, BDNF is linked to major depressive disorder.