In the brain of SDS mice with ongoing symptoms of depression, NGF protein levels were significantly enhanced [F(3, 28) = 4.619710, p = 0.0095] (Control vs. SDS, p < 0.01), and BDNF [F(3, 28) = 8.565, p = 0.0003] (Control vs. SDS, p < 0.01), NT-3 [F(3, 28) = 6.331818, p = 0.0020] (Control vs. SDS, p < 0.01), and NT-4/5 [F(3, 28) = 6.155, p = 0.0024] (Control vs. SDS, p < 0.01) levels were significantly suppressed (Figure 9). Here, NGF is linked to depressive disorder.