Scientists have identified five major phases of brain development across a human lifetime, with research suggesting that the brain does not fully enter its “adult” mode until around the early 30s.
The findings come from a large study of brain scans from nearly 4,000 people ranging in age from under one year old to 90. Researchers found that brain development shifts at four key “turning points”, occurring at roughly ages nine, 32, 66 and 83, creating five distinct brain “epochs”.
The first phase, childhood, runs from birth to about age nine and is marked by rapid growth but also “pruning” of neural connections, where weaker links are lost and stronger ones are reinforced. During this time, brain wiring becomes less dense but more specialised, while brain structures such as grey and white matter grow quickly.
The second phase, adolescence, extends from around age nine into the early 30s. In this era, white matter continues to grow and brain networks become more efficient, which is linked to improved cognitive performance. This period is also when many mental health conditions are most likely to first appear.
Around age 32, the brain undergoes its strongest shift, entering a long adult phase that can last over three decades. During this time, brain structure becomes more stable and compartmentalised, matching a general plateau in intelligence and personality described in other research.
A third turning point occurs around age 66, marking the beginning of an “early ageing” phase. The final phase, starting at roughly age 83, is considered “late ageing”, when brain connectivity declines further due to degeneration of white matter.
Researchers say understanding these turning points could help scientists identify when the brain is most vulnerable to disruption, disease or mental health disorders, and better understand how our brains change throughout life.
