Research Has Finally Put the Nature Vs. Nurture Debate to Rest

It’s one of the greatest debates in psychology – and something we’ve been debating ourselves since our high school social studies class. 

Now, there may finally be a solid(ish) answer to the whole nature vs. nurture debate. 

When it comes to whether our traits are influenced by genetic or environmental factors, in-depth research on 50 years of studies on twins has revealed that it’s pretty much a draw. 

Not that we’re surprised. 

Researchers gathered 2,748 studies involving more than 14.5 million pairs of twins and found the average variation for human traits and disease is 49% due to genetic factors and 51% due to environmental factors.  

The studies were published between 1958 and 2012 and used “classical twin design,” comparing the similarities of identical twins who share all their genes to those of fraternal twins who only share half their genes. Meaning, traits that correlated more closely in the fraternal twins compared with identical twins signified a greater influence of environmental factors.

More than 50 per cent of the studies were related to psychiatric, metabolic, and cognitive functions. This included rates of depression, anxiety, mental and behavioural disorders related to use of alcohol and tobacco, weight and height. 
Despite the five decades of in-depth twin studies, there has still been considerable debate in the whole nature vs. nurture department. The new study reveals, though, that the dialogue should move away from the “either/or” debate and toward how the two can work together to form an individual. 

It should be noted, however, that, though the studies averaged an almost even split between genetic and environmental factors, there was in fact wide variation within the 17,800 separate traits and diseases examined by the studies.

For example, weight maintenance was found to be 63 per cent due to genetics and 37 per cent due to environmental factors, and the risk for bipolar disorder was found to be 68 per cent due to genetics and only 32% due to environmental factors.  

On the other hand, the risk for developing eating disorders was found to be 40 per cent genetic and 60 per cent environmental, and the risk for mental and behavioural disorders due to use of alcohol was 41 per cent genetic and 59 per cent environmental.

Not shockingly, when it came to psychiatric, ophthalmological and skeletal traits, genetic factors played more of an influential role than environmental factors. When it came to social values and attitudes it was the other way around.

In an interesting find, there was no single trait in which the influence of genetic factors was zero (so, you may want pick the person you’re going to procreate with wisely). Genetics have an influence in all traits – the difference lies in how prevalent. 

So, you can blame your parents, grandparents, and great grandparents…

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