In a study of breast cancer survivors (Lengacher et al. 2015), individuals who were homozygous for the common G allele (GG) in solute carrier family 6 member 4 (SLC6A) rs16965628 had greater improvements in three cognitive outcomes (i.e., memory, organization, global cognition) compared to individuals who were heterozygous or homozygous for the rare C allele (GC or CC). Here, SLC6A4 is linked to breast cancer.