Interpreting Polygenic Prediction of Cognitive Ability: Evidence for Direct, Reliable, and Portable Genetic Effects

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This week, the ICA Journal published a major article by Herasight scientists (Tobias Wolfram et al.) on using “polygenic scores” (scores based on a person’s DNA, abbreviated PGS) to predict intelligence, health diagnoses, and life outcomes. Here’s a quick summary of their findings:

:right_arrow: The PGS predicted intelligence pretty well: r = .45. (To put this in perspective, socioeconomic status usually predicts IQ at r ≈ .20 to .30).
:right_arrow: Higher PGSs for IQ also predicted better higher occupational prestige (2nd image) and better mental health outcomes (3rd image).
:right_arrow: The PGSs were less predictive for people with non-European ancestry (especially African Americans), which is expected.
:right_arrow: The PGSs were equally predictive across the range of socioeconomic statuses (4th image), which is evidence against the Scarr-Rowe effect that predicts that genes will have a weaker influence in low-SES individuals than middle- and upper-class individuals.

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These findings have major practical and theoretical implications. From a practical perspective, Herasight is an embryo selection company. This study means that when their customers select the smartest embryo during in vitro fertilization, they are also generally picking a future child that has better mental health and a more prestigious occupation as an adult. It sounds like sci-fi, but it is reality today.

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From a theoretical perspective, this study reveals a lot about the genetic architecture of the psychological traits: generally, the same genes that make a brain smarter also make it less susceptible to mental health diagnoses.

Link to original post: https://x.com/RiotIQ/status/2042993325360451824?s=20

Link to full article: https://icajournal.scholasticahq.com/article/158459-interpreting-polygenic-prediction-of-cognitive-ability-evidence-for-direct-reliable-and-portable-genetic-effects

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What you are describing is called pleiotropy, which is when the same genetic variants influence multiple traits simultaneously. The Herasight study mapped PGS for general cognitive ability against 20 different psychological and neurodevelopmental outcomes and found a pretty clear pattern. Higher cognitive PGS was associated with lower ADHD symptoms, lower psychosis risk, lower manic traits, and better self-regulation. The scatter plot in the study shows these associations cluster tightly around the line you would expect if the PGS was operating through actual cognitive ability rather than through some separate pathway.

The occupational finding is also striking. Across a wide range of jobs, higher average PGS in a profession corresponded very cleanly with higher occupational status, from heavy goods drivers at the low end to medical practitioners and lawyers at the high end. The gradient is remarkably linear. This makes sense if you think of g as a generalized problem solving resource that gets deployed across different life domains. The same underlying architecture that supports faster learning and better reasoning also appears to reduce vulnerability to certain psychiatric conditions. They are not separate things being influenced separately, they are downstream effects of the same genetic profile.

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It also explains why IQ correlates with so many life outcomes beyond academics. The g factor was always described as broad for a reason. The genetic data is starting to show why that breadth exists at a biological level.