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. 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. 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.