BDNF and Down syndrome: Among Down's syndrome patients, BDNF level increases in old (>60 years old) patients (69.83 ± 22.15 SD pg/mL) compared to both children (2-14 years old, 36.94 ± 22.15 SD pg/mL with p < 0.01) and adults (20-50 years old) Down's syndrome patients (44.98 ± 21.34 SD pg/mL with p < 0.01).