Most common diseases result from interplay between genes and environment, although the relationship between these factors is not always clear. Three recent papers[1-3] tackle the relationship between genetics, smoking, and smoking-related diseases like lung cancer, yet they come to different conclusions: One suggests that a locus influences smoking behavior, which in turn affects lung cancer; while two others suggest that the same locus influences lung cancer independently of smoking.
Although smoking rates are on the decline, 21% of all adults (45 million people) in the United States smoke cigarettes.[4] In addition to being the primary cause of lung cancer, smoking also influences heart disease, with smokers increasing their risk for coronary heart disease by 2-4 times compared with nonsmokers.[5] Despite these strong associations, however, not all individuals who smoke will go on to develop these diseases. Genetics may play a role here, making some individuals more susceptible by increasing their risk for disease or through influencing smoking behavior itself.