Study finds Five Major Brain Development Phases, Adulthood Actually Begins 32 - Video

The human brain doesn't just grow up overnight-it evolves in five distinct stages, each packed with its own unique changes and challenges. Researchers at the University of Cambridge analyzed brain scans from nearly 4,000 people aged from birth to 90, revealing that brain development and ageing follow a complex, non-linear journey. Their work, published in Nature Communications, identifies major milestones around ages 9, 32, 66, and 83 that mark shifts in how our brain’s wiring adapts throughout life.

Using advanced imaging to track how water moves through brain tissue, the team reconstructed the brain’s wiring diagram at different ages and measured how efficiently regions communicated with each other. This allowed them to spot four sharp “topological turning points” that mark transitions between five phases: childhood (0–9), adolescence (9–32), adulthood (32–66), early ageing (66–83) and late ageing (83+). The patterns held up across thousands of scans, even though the exact timing varied a little from person to person.

In the first stage-childhood, from birth to nine years-the brain rapidly expands and prunes connections. Dr. Alexa Mousley, lead author, describes this as a noisy, inefficient communication phase where the brain explores a wide range of connections before settling on the most efficient pathways.

Around nine years old, the brain hits a dramatic “rewiring” phase lasting into the early thirties-far beyond what was traditionally called adolescence. During this phase, neural pathways strengthen, becoming highly efficient and boosting peak cognitive performance typically seen in the early 30s. This period is also when many mental health conditions first emerge, possibly linked to the intense brain remodeling underway.

From 32 to 66 years, brain wiring changes slow significantly, marking a plateau in intelligence and personality development—what many recognize as stable adulthood. But then, around age 66, early ageing begins. The brain’s network starts to fragment into distinct clusters rather than a single integrated system. This shift coincides with increased prevalence of dementia and cardiovascular conditions affecting cognition.

Finally, after age 83, this modularity intensifies-certain brain regions become critical hubs, and overall connectivity changes further. These detailed brain “epochs” help explain why different cognitive and neurological conditions emerge at specific life stages and could guide personalized strategies to maintain brain health throughout our lives.

This groundbreaking study reshapes our understanding of brain lifelong development and ageing, highlighting the dynamic and ever-changing nature of our neural wiring.

REFERENCE: Mousley, A., Bethlehem, R.A.I., Yeh, FC. et al. Topological turning points across the human lifespan. Nat Commun 16, 10055 (2025). https://doi.org/10.1038/s41467-025-65974-8