These strong genetic findings for nicotine dependence now allow us to increase our knowledge on how genetic risk factors influence nicotine dependence and comorbid psychiatric disorders. For instance, we can test whether these genetic variants in the chromosome 15 region which increase the risk for developing nicotine dependence are also associated with commonly comorbid disorders such as alcohol dependence and major depressive disorder. In addition, we can test whether or not comorbid psychiatric disorders moderate the genetic risk for nicotine dependence. Potential genetic risk moderation is important from both etiologic and preventive standpoints (Hunter, 2005). It can provide clues about how genetic variants may affect the disease risk, through potential interactions with other genetic or environmental factors associated with a comorbid disorder. In addition, this work can help identify subpopulations that are more susceptible to the genetic risks. For example, depressed individuals may be at increased genetic risk for developing nicotine dependence.
