In veterans with PTSD who smoked, BDNF rs56164415 was associated with cognitive decline in smokers in the genotype (H = 10.729; df = 2; p = 0.005), dominant (U = 9327.0; p = 0.003), and allelic (U = 24113.5; p = 0.011) model (Figure 2, Supplementary Table S2). The gene discussed is BDNF; the disease is post-traumatic stress disorder.