Platelet MAO-B activity was significantly (Kruskal–Wallis ANOVA) increased (p < 0.001, Dunn’s test) in smokers (H = 24.60; p < 0.001) and in non-smokers (H = 39.53; p < 0.001) with PTSD when compared with corresponding veterans without PTSD, but did not differ when compared with control subjects (Figure 1). The gene discussed is MAOB; the disease is post-traumatic stress disorder.