Risky business lies in your genes

15 January 2019

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Are you a daredevil or do you prefer to play it safe? Whatever your answer, while you might think you freely choose whether to take risks or follow the rules, new research shows that your genes could be pulling some strings, influencing your choices and your appetite for adventure and risk.

A study that delves into the genes of over a million people has identified 124 genetic variants located on 99 separate regions of the genome associated with risky behaviour. It also sheds new light on which areas of the brain are involved in influencing risk tolerance, and improves our understanding of how genetic and environmental factors sway us to make (or avoid!) taking risks.  

Brain areas and chemicals involved in risk  

The study, published in Nature Genetics, was led by Assistant Professor Jonathan Beauchamp from the University of Toronto and Dr Richard Karlsson Linnér from Vrije University Amsterdam, and involved contributions from IMB researchers including Professor Jian YangDr Jacob Gratten, Dr Maciej Trzaskowski, Dr Yang Wu and Dr Futao Zhang.

“There’s a wide range of willingness to take risks across individuals,” Professor Yang said. “We all know people who are prepared to live life on the edge, and others who minimise risk as much as possible. While non-genetic factors may be the major determinant of our willingness to take risks, what has previously been unclear is what role our genes do play in risk taking, and which areas of the brain are involved.

“Risk taking has been extensively studied in the social sciences, and there have been some previous genetic studies with relatively small sample sizes, but this study is by far the largest to date, looking at a combined sample of over one million people of European ancestry.

“Our results directly contradict previous thinking on the biological pathways involved in risky behaviour. Prior research has focused on the pathways associated with the chemicals cortisol, dopamine, serotonin, estrogen and testosterone. We found no evidence that general risk tolerance was more strongly associated with genetic variants near genes involved in these pathways than other genes. 

“Conversely, we did uncover evidence that other chemical pathways and areas of the brain not previously associated with risk taking are actually statistically likely to be involved.”

The researchers found that the chemicals glutamate and GABA are likely to play a role in taking risks. These are both neurotransmitters, chemicals that carry messages from neurons, with glutamate being the main neurotransmitter that causes neurons to fire, known as an excitatory neurotransmitter, while GABA is the brain’s main inhibitory neurotransmitter, causing neurons to decrease their activity. 

Brain regions that appear to be involved in risk were the prefrontal cortex and the basal ganglia, which are involved in the primate reward system, which is “critically involved in learning, motivation and decision-making, notably under risk and uncertainty,” the researchers wrote. “We do caution, however, that our results do not point exclusively to the reward system.” There was also evidence for roles in tissues of the central nervous system and the immune system, though the researchers noted “future work would be needed to confirm this result and uncover specific pathways that might be involved.”

General risk tolerance vs specific risks

The main trait the researchers examined was general risk tolerance, an individual’s self-described tendency to take risks. They also studied people’s self-reported adventurousness, and their likelihood of engaging in four specific risky behaviours: speeding, drinking, whether they had ever smoked and their number of sexual partners.

Previous research had suggested that a person’s propensity to take a risk in one domain did not necessarily translate to their likelihood of taking risks in different domain. For example, the thinking was that someone who quit a stable job to start a business might not necessarily be comfortable jumping off a cliff into the ocean. 

But this study found that, in fact, the genetic correlations between a general tolerance for risk and specific risky behaviours were comparatively large, suggesting that differences in whether an individual actually engaged in different types of risky behaviour was partly down to the same set of genetic factors.

Assistant Professor Beauchamp said, “Genetic variants that are associated with overall risk tolerance — a measure based on self-reports about individuals’ tendencies to take risks in general — tend to also be associated with more speeding, drinking, tobacco and cannabis consumption, and with riskier investments and sexual behaviour.”

Influence of sex and age, and overlap with other traits and diseases

Stereotypes suggest that males are more likely to take risks than females, and indeed, many more males than females in the study identified as risk tolerant, with more than a third of males describing themselves this way compared to just under a fifth of females.

Although males in general might be more willing to engage in risks, the genetic correlations between females and males contributing to general risk tolerance were found to be similar between the sexes, though not identical, meaning that differences in general risk tolerance between females are influenced by similar genetic factors as those between males. The researchers also show that general risk tolerance declines with increasing age.

The researchers also identified significant genetic correlations between risk tolerance and non-risk related traits.

“We also found shared genetic influences on overall risk tolerance and several personality traits and neuropsychiatric traits — including ADHD, bipolar disorder, and schizophrenia,” Beauchamp said.

Future implications

Overall, the researchers highlighted that each genetic variant on its own will have little effect. But taken together and in conjunction with environmental factors, they build a picture of why we take risks. 

While the researchers cautioned that the results can’t be used to meaningfully predict an individual’s tolerance for risk or their risk-taking behaviour, they expect it to be useful in social science studies, such as studying how genetic factors interact with environmental variables.

So, next time you go to plant the foot on the accelerator, or take a swig of your favourite alcoholic tipple, stop and consider the genes and biological pathways in your brain lighting up, and helping to influence your decision.

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