Do you live life close to the edge? Climb mountains free-style, jump off bridges with small gliding parachutes, have unprotected sex with strangers, or even discuss genetic differences in public meetings? Further, have you been so busy living in the vivid present that you have no savings and no pension, and expect others, who are living boring lives doing dull work, to pay your bills and provide for your old age? If so, and you can bother to pause for a moment to do some reading, here is an interesting study to ponder. Ponder means to think about something carefully, taking your time about it.
Title: Genome-wide study identifies 611 loci associated with risk tolerance and risky behaviors
Linner et al say:
Humans vary substantially in their willingness to take risks. In a combined sample of over one million individuals, we conducted genome-wide association studies (GWAS) of general risk tolerance, adventurousness, and risky behaviors in the driving, drinking, smoking, and sexual domains. We identified 611 approximately independent genetic loci associated with at least one of our phenotypes, including 124 with general risk tolerance. We report evidence of substantial shared genetic influences across general risk tolerance and risky behaviors: 72 of the 124 general risk tolerance loci contain a lead SNP for at least one of our other GWAS, and general risk tolerance is moderately to strongly genetically correlated (r= 0.25 to 0.50) with a range of risky behaviors. Bioinformatics analyses imply that genes near general-risk-tolerance-associated SNPs are highly expressed in brain tissues and point to a role for glutamatergic and GABAergic neurotransmission. We find no evidence of enrichment for genes previously hypothesized to relate to risk tolerance.
They looked at self-assessed risk tolerance, and also risk-taking in automobile speeding, drinking, smoking and number of sexual partners. As per usual, the subjects were European-ancestry subjects. At some stage other ancestries will be studied, I presume, or perhaps not. Once again, these are gigantic sample sizes, and must have taken years and countless meetings and conferences to organize. A bit harder than asking all 60 of your students to fill in a questionnaire.
We also estimated genetic correlations between general risk tolerance and 28 additional phenotypes. These included phenotypes for which we could obtain summary statistics from previous GWAS, as well as five phenotypes for which we conducted new GWAS. The estimated genetic correlations for the personality traits extraversion (r= 0.51), neuroticism (r=0.42), and openness to experience (r=0.33) are substantially larger in magnitude than previously reported phenotypic correlations pointing to substantial shared genetic influences among general risk tolerance and these traits.
Our results provide insights into biological mechanisms that influence general risk tolerance. Our bioinformatics analyses point to the role of gene expression in brain regions that have been identified by neuroscientific studies on decision-making, notably the prefrontal cortex, basal ganglia, and midbrain, thereby providing convergent evidence with that from neuroscience. Yet our analyses failed to find evidence for the main biological pathways that had been previously hypothesized to influence risk tolerance. Instead, our analyses implicate genes involved in glutamatergic and GABAergic neurotransmission, which were heretofore not generally believed to play a role in risk tolerance.
The authors add a cautionary note:
Across the risky behaviors we study, we find that the genetic correlations are considerably higher than the phenotypic correlations (even after the latter are corrected for measurement error) and that many lead SNPs are shared across our phenotypes. These observations suggest that the low phenotypic correlations across domains are due to environmental factors that dilute the effects of a genetically-influenced domain-general factor of risk tolerance.
So, what can we conclude from the genetic correlations? Tentatively, that the “genes for” risk taking are associated with the “genes for” having intercourse early in life, having babies while still a teenager, using cannabis and being self-employed (which must cover a wide range of activities); slightly associated to educational attainment and cranial volume, somewhat to ADHD, anxiety disorders, bipolar disorder and schizophrenia, and also to extraversion, openness to experience and to stability, and to household income. This is an interesting constellation of features, and mostly conforms to pattern for “fast life histories” so beloved of evolutionary researchers. It would be interesting to know if these risk-takers have pensions and savings. I assume not. Of course, these are correlations between the genes for one thing (risk-taking) and the genes for other things (attitudes and lifestyles) but in reality the links between the genes for risk-taking and all the other measures are slight in reality. Other factors intervene.
This is a crucial point. Studies like these can point to associations between genes and behaviour. This one has a strong story to tell, one which hangs together and makes sense. Yet, it has low predictive value at the moment. Perhaps risk-taking really does depend on getting into bad company (that is, it requires the amplifying effect of being with other risk-takers for a critical mass of dare-devils to spin into dangerous activities). Could such vulnerable young persons be saved by joining the Boy Scouts? Possibly. Some cultural practices might channel risk-takers into pro-social actions, while other cultural practices let them drift into trouble.
As per usual, the percentage variance accounted for is very small, 1.6% at best. This is the best genetic research ever done on this topic, and yet in future it might be seen as only a starting point, so fast is the genetic field progressing.
Here is a thing, which I could not find directly addressed in the paper. Yes, the subjects of this study are risk takers, but in fact only mildly so. Driving fast, smoking, drinking, and having lots of sex with different people all have their risks, and their pleasures, but they are small beer. The main point is: the real risk takers probably fell out of the gene pool long ago. We are dealing with some of their surviving children, and a vast mass of more cautious survivors.