string: clarified that no association between ApoE and BDNF genotypes has been established (20, 21, 25, 31, 33-35, 37), although it has been suggested that the C270T-T allele is more common among individuals lacking ε4 (19), and the risk of AD conferred by the C270T-T allele is stronger in patients who do not carry ε4 (23).