BDNF and Parkinson disease: However, the serum levels of mBDNF and mBDNF/proBDNF ratio were significantly lower in the ex-PD group than in the ex-NPD group (19.73 ± 7.31 vs. 23.47 ± 8.21 ng/ml for mBDNF, t = 2.794, df = 154, p = 0.0059; 0.09 ± 0.05 vs. 0.15 ± 0.12 for mBDNF/proBDNF, t = 4.216, df = 154, p < 0.0001).