Change in the serum BDNF between weeks 0 to 12 was significantly larger in the non-distress group than in the distress group, who met the criteria for PTSD or major depression (median, 33.5; range, 8.5-56.0 vs. median, 5.4; range, 4.4-6.4, p = 0.037). Here, BDNF is linked to major depressive disorder.