In their study of adolescents, Pallavi et al. noted that treatment naïve adolescents with depression (n = 64) had significantly lower mean serum BDNF levels as compared with healthy controls (n = 64) (8.27 ± 0.39 vs. 10.30 ± 0.39 ng/ml; p < 0.001). Here, BDNF is linked to depressive symptom measurement.