Cigarette smoking remains a leading cause of preventable disease and premature death in many countries. The chance that a lifelong smoker will die prematurely from complications due to smoking is approximately 50%. There is an increasing interest in understanding the genetic link to nicotine dependence in order to better predict who is at risk and what steps can be taken to mitigate that risk. In a collaborative effort, scientists at Oregon Research Institute and SRI International are studying the interaction between specific candidate genes associated with the stress/reward pathway and both early life adversity and ongoing life stress. The investigators are also seeking to identify salivary biomarkers of life stress, comparing those who have experienced high life stress with those who have experienced little, through an analysis of an individuals’ RNA. This may help to explain the success or failure of interventions designed to prevent the initiation of tobacco use and the progression to nicotine dependence.
Four hundred participants in an ongoing longitudinal study participated in an intensive assessment at age 20 to 23 years old. Participants in the study take part in a laboratory stress test where saliva samples are collected for cortisol analysis over a 90 minute period. They participate in a clinical interview obtaining a diagnosis for substance use, abuse, and dependence, as well as depression and anxiety. The participants also complete a questionnaire. Finally, the research team obtains a measure of early life adversity and a measure of ongoing life stress via a one-on-one interview with the participants.
The study includes both DNA and RNA collection using Oragene and Oragene•RNA respectively. Saliva collection for DNA extraction is to assess polymorphisms of candidate genes known to be related to the stress-reward pathway. Saliva collection for RNA extraction is for candidate gene and genome wide gene expression. Saliva-based collection with Oragene was a natural choice for this project. Up to 74% of the DNA in saliva comes from white blood cells, yielding virtually the same amount of DNA per volume and the same DNA quality as blood. This is yet more evidence that saliva can be considered a good and reliable source of DNA for a wide variety of genetic applications.
The outcome of this ongoing project is not yet known but this study has the potential to uncover an important genetic link to nicotine dependence. We wish them the best of luck.
 Doll R, Peto R, Boreham J, Sutherland I.Mortality in relation to smoking: 50 years observations on male British doctors. BMJ 2004;328:1519.
 Thiede, C. et al. Buccal swabs but not mouthwash samples can be used to obtain pretransplant DNA fingerprints from recipients of allogeneic bone marrow transplant. (2000). Bone Marrow Transplantation. 25(5): 575-577.)