Cigarettes and coffee: a deadly combination?

Over the summer, the RAD bloggers are taking some time off for a well-deserved holiday. To keep you up to date with interesting topics relating to smoking, alcohol, drugs and diet, we will be sharing some of our past blog posts and sci-flies with you again.

*Disclaimer: Please note that parts of this sci-fly have been automatically translated.*

Can’t get through the day without a few (or more) cups of coffee? Then you might be more likely to become addicted to nicotine. We already know from scientific research that our behaviour is influenced by genetic factors (the DNA you’re born with). Virtually every trait, from weight to psychological problems, is partly determined by your genes¹. This also applies to addictive behaviour, such as smoking cigarettes or drinking large amounts of caffeinated coffee. New research now shows that the genetic risk factors for these two addictions are partly the same.

Nicotine and caffeine are the most commonly used stimulants worldwide. Smokers consume more caffeine than non-smokers or people who have stopped smoking². You may well have noticed this in your immediate surroundings. The question is: why is this? It was already known that differences between people in starting to smoke are determined by genetic factors by 44%, and the extent to which someone subsequently becomes addicted to cigarettes by 75%_³. In my PhD research, I found that drinking a lot of caffeine (more than 5♀ or 6♂ cups of coffee a day) is genetically determined by about 50%. Even more striking was that a large proportion of the genes that increase the risk of smoking also increase the risk of consuming large amounts of caffeine⁴.

We do not yet know exactly which genes are responsible for this increased risk of both smoking and caffeine consumption. Obvious candidates are genes related to the brain’s reward system. This reward system has evolved to make you feel good when you engage in behaviour that is beneficial to you. It kicks in, for example, when you eat, which makes sense, as you need food to survive. However, addictive substances such as nicotine and caffeine also activate this system. As a result, people will want to use them time and time again, and some people will become addicted to them. Some people will be genetically more susceptible to this than others.

Of course, none of this means that you have no control over your own behaviour. First and foremost, you can always choose not to take up a particular addictive behaviour, such as smoking. And, although it is difficult, it is certainly possible to quit, regardless of your genetic risk of addiction. In the same way, you are in control of your own caffeine intake. Although my PhD research took up a great deal of my energy over four years, I managed it without coffee and the associated caffeine boost. This wasn’t actually a conscious choice, but simply because I find coffee disgusting. But then again, I don’t smoke cigarettes either, so those risk genes for addictive behaviour probably aren’t too much of a concern for me!

References

1. Polderman, T.J.C., Benyamin, B., De Leeuw, C.A., Sullivan, P.F., Van Bochoven, A., Visscher, P.M., & Posthuma, D. (2015). Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nature Genetics, 47(7):702-709. https://doi.org/10.1038/ng.3285
2. Treur, J.L., Taylor, A.E., Ware, J.J., McMahon, G., Hottenga, J., Baselmans, B.M.L., Willemsen, G., Boomsma, D.I., Munafò, M.R., & Vink, J.M. (2016). Associations between smoking and caffeine consumption in two European cohorts. Addiction, 111(6), 1059-1068. https://doi.org/10.1111/add.13298
3. Vink, J.M., Willemsen, G., & D.I. Boomsma (2005). Heritability of smoking initiation and nicotine dependence. Behavior Genetics, 35(4):397-406. https://doi.org/10.1007/s10519-004-1327-8
4. Treur, J.L., Taylor, A.E., Ware, J.J., Nivard, M.G., Neale, M.C., McMahon, G., Hottenga, J., Baselmans, B.M.L., Boomsma, D.I., Munafò, M.R., & Vink, J.M. (2016). Smoking and caffeine consumption: a genetic analysis of their association. Addiction Biology, 22(4), 1090-1102. https://doi.org/10.1111/adb.12391

This blog was written on the 15th of April 2016 by Dr. Jorien Treur (Radboud University) for RAD-blog, the blog about smoking, alcohol, drugs and diet.