Nature v. Nurture – Smoking and Other Complex Problems

A long-standing debate in the life sciences has been the role of nature versus nurture in determining individual characteristics. For example, how much of an individual’s height is determined by their genes and how much by their nutrition – both in childhood and prenatally?

In the last few decades advances in our understanding of genetics has shifted this dichotomy to describe it in terms of genetics versus environmental factors, and expanded our appreciation for the role nature/genetics play in causing all manner of human diseases. For example, it was discovered that genetically determined slow serotonin transporters in the brain can predispose individuals to developing depression. However, the more we learn about genetics, similarly exciting discoveries are being made into how environmental factors influence the activity of genes, and thus affect an individual’s health.

Thus – like many things with multifactorial causes – the pendulum swings one way and then the other, i.e. between nature/genetics and nurture/environment.

Pendulum

But what has also become clear is that genetics and environmental influences are not  separable – they interact in important ways, and both can cause health problems and be routes to solutions too.

What recently caught my eye in the nature versus nurture debate were two studies about smoking cessation that came out in the last couple of weeks. The first, by Nicholas Christakis published in the New England Journal of Medicine (and reported in the May 22nd New York Times) describes the importance of social factors for people trying to quit smoking. This study demonstrates how an individual’s social environment plays a dramatic role in their ability to stop smoking, and how people can help each other stop smoking as a collective activity.

On the nature side of the equation, NIH researcher George Uhl led a study that shows how genetic markers can predict which of two smoking cessation treatments will be more likely to work for an individual. From these two studies it is also possible to postulate that individuals may have genetic predispositions that effect the ability of social networks to help them to stop smoking – or possibly to start smoking in the first place. (Didn’t we call this peer-pressure in junior high?)

I find both these studies very interesting because for years smoking has often been described in terms of individual choice (or weakness), and as such something that is completely separate from genetic or environmental factors. These studies refute that popular myth, and more generally illustrate the fundamental point that most illnesses and healthcare problems are complex, and that the solutions to these problems need to be similarly sophisticated. This also reminds me why I cringe a bit when someone says to fix a healthcare problem, “all we need to do is…….”

What are your favorite examples of interacting genetic and environmental factors, or where simple solutions have gone awry when used for complex problems?

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