Charting child development using adult polygenic scores

In our study, we focused on two of the most powerful polygenic scores currently available: one for cognitive ability (often called intelligence) and one for educational attainment (years of schooling). We combined these into a single score and used it to track development in more than 10,000 individuals from early childhood (around age 2) to adulthood (age 26).

Because DNA is fixed at conception, these scores provide a unique opportunity: we can use a score derived from adults to look backwards and examine how early in life it begins to predict development.

What we found

We found that these adult-based genetic scores are already predictive of cognitive ability as early as age 2, although the effects are small. Their predictive power increases steadily across development, reaching about 12% of the variance explained in cognitive ability by early adulthood.

In contrast, predictions for behavioural traits and physical characteristics (such as height and body mass index) were much smaller, though still statistically reliable, explaining up to about 3% of the variation.

Furthermore, these genetic scores were not only related to outcomes at specific ages but also to developmental trajectories over time. Children with higher polygenic scores tended to:

• Start off with slightly higher cognitive and educational performance in early childhood, and
• Show a modest but consistent increase in their relative standing over time compared to their peers.

The prediction of developmental trajectories was the strongest for educational outcomes. However, links between these genetic scores and behavioural development were less consistent and did not follow a clear pattern.

A complex picture

Despite their predictive power, it is crucial to interpret these findings carefully. Polygenic scores are predictors, not causes. They do not directly determine a person’s abilities or life outcomes. Instead, they reflect a complex interplay between genes and environments. For example, individuals growing up in the same family often share both genetic similarities and environmental advantages, making it difficult to separate these influences.

In addition, these scores likely capture not only cognitive abilities but also non-cognitive traits, such as motivation, persistence, and other characteristics that contribute to success in education.

The takeaway

Overall, polygenic scores are among the strongest predictors we currently have for cognitive and educational outcomes. However, they should not be mistaken for explanations of how or why these outcomes arise. Understanding development requires considering both genetic influences and the environments in which people grow up.