This 2022 human study investigated healthy young adult brain changes using MRI and epigenetic clock technologies:

“We aimed to characterize the association of epigenetic age (i.e. estimated DNA methylation age) and its acceleration with surface area, cortical thickness, and volume in healthy young adults. It is largely unknown how accelerated epigenetic age affects multiple cortical features among young adults from 19 to 49 years. Prior findings imply not only that these dynamic changes reveal different aspects of cortical aging, but also that chronological age itself is not a reliable factor to understand the process of cortical aging.

Seventy-nine young healthy individuals participated in this study. Findings of our study should be interpreted within the context of relatively small sample size, without older adults, and with epigenetic age assessed from saliva.

Additional and unique regional changes due to advanced and accelerated epigenetic age, compared to chronological age-related changes, suggest that epigenetic age could be a viable biomarker of cortical aging. Longitudinal and cross-sectional studies with a larger sample and wider age range are necessary to characterize ongoing effects of epigenetic cortical aging, not only for healthy but also for pathological aging.”

https://doi.org/10.1093/cercor/bhac043 “The effects of epigenetic age and its acceleration on surface area, cortical thickness, and volume in young adults” (not freely available) Thanks to Dr. Yong Jeon Cheong for providing a copy.