Risky Brains: Brain Structure Promotes Smoking, Drinking, Sex

New study finds structural differences in brains of risk takers--blame parents

Posted Feb 01, 2021 | Reviewed by Lybi Ma

Image by John Glassberg / Wikimedia Commons Public Domain
Source: Image by John Glassberg / Wikimedia Commons Public Domain

Our survival requires balancing risk against reward, but some people take risks with abandon whereas others cower. Why?  Consider elite rock climber, Emily Harrington, who became the first woman to free climb the extremely dangerous route Golden Gate, on El Capitan in a day, triumphing only a year after she suffered a near-fatal fall on the same route. According to new research, the brains of risk-takers are anatomically different. This raises the intriguing question of whether risky brain anatomy is sculpted by daredevils engaging in risky business, or instead, a risk-taker’s fate is cast at birth by genetics. The new study, published this week in Nature Human Behavior offers answers to both of these questions, giving possible insight not only into thrill-seekers like Harrington but also into the minds of people who take more common risks, like substance abuse and sexual promiscuity.

The link between risk-taking and brain structure has sparked experimental interest before, but the studies to date have been relatively small, rendering the observations less conclusive. This new study was made possible by an enormous public database of MRI images of people assembled together with personal medical information. An international team of researchers, headed by Gideon Nave at the University of Pennsylvania, analyzed brain scans from 12,675 people in the United Kingdom in association with their propensity to engage in four risky behaviors: drinking alcohol, smoking, speeding, and sexual promiscuity. 

The population that met these criteria was also found to be more likely to use cannabis, be self-employed, have attempted suicide, engaged in antisocial behavior, be extraverts, and have had their first sexual experience at an earlier age. The researchers were careful to weed out other factors that are known to be associated with brain anatomy, including age, gender, level of education, IQ, handedness, body size, and other possible confounds. The screen showed that the brains of people who met these risk-taking criteria had smaller tissue volumes in several specific brain regions. These included the amygdala, important in emotion and threat detection, the hypothalamus involved in the ‘fight-or-flight’ response, regions of the prefrontal cortex, important in higher-level decision-making, emotional regulation, and impulse control. All of these regions were smaller than average, and interestingly, the study found no brain regions in risk-takers that were larger than average. 

Soon after the researchers completed their analysis in February 2020, the database released information from many more participants, which provided the researchers an opportunity to replicate their findings with an independent set of data from 13,005 people. Their primary findings did indeed replicate. 

The maxim in architecture that ‘form follows function,’ also applies to biology. Indeed when the researchers analyzed another large public database of functional MRI, which monitors patterns of functional activity in the brain, the researchers found that in a group of 4,717 participants who were classified as engaging in risky behaviors, brain function differed from average in some of the same anatomical regions that were smaller than average in the brains of risk-takers (amygdala and prefrontal cortex). 

Knowing that the brain, behavior, and biology in general, are determined by both our genes and our unique experiences, the question arises as to whether these brain differences that correlate with risk-taking are caused by engaging in risky activities or are instead the result of genetic factors. The researchers were able to address this by analyzing data from another large publicly-available database of genetic information derived from an independent sample of 297,025 participants. They found that the genetic risk scores derived from collections of genes associated with risky behavior were associated with the reduced brain volume in the prefrontal cortex and hypothalamus. The study concludes that neuroanatomical features in the brains of risk-takers are in large part inherited. 

The genetic link does not exclude that there are also contributions of experience in promoting risk-taking or in contributing to the neuroanatomical differences, but it does indicate that there is a genetic propensity for risk-taking. 

That finding raises some interesting questions to ponder. Should brain scans be used to separate the bold from the meek to select individuals who are predisposed to excel in risky professions, such as in the military or police? Alternatively, could brain imaging and genetic analysis be used to identify specific strengths and weaknesses in individuals at a very young age to enable interventions that would moderate or capitalize upon strengths and weaknesses perceived in a person’s brain? Finally, how should society take into consideration culpability in antisocial behavior that is associated with risk-taking if there are biological underpinnings for the behaviors that others in society may not have? 

Maybe try bringing this scientific article with you as evidence in traffic court!  Good luck with that!