- A functional polymorphism in the succinate-semialdehyde dehydrogenase (aldehyde dehydrogenase 5 family, member A1) gene is associated with cognitive ability. Plomin, R., Turic, D.M., Hill, L., Turic, D.E., Stephens, M., Williams, J., Owen, M.J., O'Donovan, M.C. Mol. Psychiatry (2004)