APOE and Mental deterioration: Preliminary work suggests that those with a high-risk APOE genotype experience greater cognitive decline when they undergo WBRT than do those with a lower risk genotype.56 Correa et al.57,58 showed that specific SNPs in catechol-O-methyl transferase (COMT), BDNF, and dystrobrevin-binding protein 1 (DTNBP1) genes can be associated with dysfunction in a myriad of cognitive domains.