A brain scan can be turned into an estimated age—but does that number really tell us how mature a young person is? This study finds that it tracks puberty, but not reliably the thinking skills people may expect. BrainAGE is a tool that purports to evaluate brain maturity in adolescents.

It gives a person an estimated brain age that can be compared with their actual age. The key question is whether BrainAGE tracks with other signs of development during adolescence, including pubertal and cognitive development.

The study examines BrainAGE alongside pubertal and cognitive maturation in early adolescence, within two narrow age ranges. The expectation is that BrainAGE will track changes in development that are reflected in changes to brain structure, including pubertal and cognitive development.

The study also examines how stable BrainAGE is over time. The study also trained and tested BrainAGE models specifically on early adolescents. Like a tailor making clothes for one age group, these models were designed to capture the structural changes happening in those particular age ranges.

The goal was to capture changes in early adolescence rather than the broader changes occurring across all of adolescence. In the baseline group, a higher or more positive BrainAGE was related to more advanced pubertal development reported by both young people and parents.

But a higher or more positive BrainAGE was also related to lower cognition scores in this analysis. The age-specific model again linked a higher BrainAGE with more advanced pubertal development reported by both young people and parents.

Here, however, a higher BrainAGE was related to higher cognition scores. The same young person’s brain-age gap was fairly consistent over time, even though some estimates rose and others fell. This supports treating it as a meaningful individual difference, rather than simply random movement from one assessment to the next.

Using the previously validated model, BrainAGE was positively related to pubertal development across both age ranges. That association was replicated with the models created specifically for early adolescence. The brain’s estimated age was generally further ahead in young people with more advanced puberty, whether they reported it themselves or a parent did.

The gap between the highest and lowest cognition groups was much less distinct, suggesting puberty was the clearer link here. The results provide initial evidence that BrainAGE tracks with some measures of maturation, including pubertal development. But the conflicting relationships between BrainAGE and cognition lead the study to question whether these models are useful for measuring processes that are not directly biological.

BrainAGE may have promise as a clinical measure and as a research tool, but its predictions and associations need careful interpretation. Because ideas about brain maturity can affect legal and policy decisions, researchers need to be clear about what BrainAGE can and cannot tell us about different forms of maturity.

BrainAGE may capture some physical changes linked to puberty, but it is not a complete measure of maturity. For families, clinicians, and policymakers, a brain-age number needs careful interpretation rather than being treated as a verdict about a young person.