Significant additive interactions were observed between the GRS and the experience of traumatic events and neighborhood social cohesion. The association between genetic risk and smoking was greater for individuals who had experienced traumatic events in their lifetimes, and diminished for individuals who had increased social cohesion in their neighborhood (depicted in Figure 1). Moreover, higher mean numbers of cigarettes smoked per day were indicated for those with increased (+1 s.d.) genetic risk in both than in those who experienced a greater (+1 s.d.) number of traumatic events (MD between high (+1 s.d.) and low (−1 s.d.) GRS=1.22) and those who had experienced a decreased (−1 s.d.) number of events (MD=0.31), but the genetic influence was even greater for those who experienced an increased (+1s.d.) number of traumatic events (IC=0.91, P<0.05; detailed in Table 4, depicted in Figure 1a). Similarly, higher mean numbers of cigarettes smoked per day were indicated for those with increased (+1 s.d.) genetic risk in neighborhoods characterized by diminished (−1 s.d.) social cohesion (MD between high and low GRS =2.59) and in neighborhoods characterized by greater (+1
