Additionally, lower serum IGF-1 observed at the sixth week correlated with higher depression and anxiety scores.121 A study of 42 college athletes, half of whom were cleared to play after mTBI while the other half served as controls, did not establish a significant correlation between brain-derived neurotrophic factor (BDNF) in serum and saliva and their scores on DASS.122 The TBICoE study found at follow-up (mean 36.2 months post-injury) that baseline serum UCH-L1 (mean 7.5 months post-injury) was significantly associated with depression (TBI-QOL). This evidence concerns the gene BDNF and major depressive disorder.