Scientists say the human brain develops through five distinct “eras” across a lifetime, with full adult brain organisation not beginning until the early 30s.
In a large study analysing brain scans from nearly 4,000 people aged from infancy to 90, researchers found that brain development follows broad phases separated by four key turning points, occurring at around the ages of nine, 32, 66 and 83.
The first phase, childhood, lasts from birth to about age nine. During this time, the brain rapidly grows and refines itself by trimming unused neural connections, while grey and white matter grow and the brain’s surface folds stabilise.
The second era, adolescence, stretches from childhood into the early 30s. In this period, white matter continues to grow and connections across the brain become more efficient, supporting improvements in thinking and cognitive performance. Researchers say this stage is defined by patterns of change rather than a fixed brain “type”.
At around age 32, the brain enters its longest phase: adulthood. This stage is marked by greater stability in brain structure, with networks becoming more compartmentalised and overall development levelling off. Scientists believe major life events, such as becoming a parent, may influence changes during this time.
A third turning point at roughly 66 marks the beginning of “early ageing”, while a fourth at about 83 signals “late ageing”. These later phases are characterised by declining brain connectivity, likely linked to the degeneration of white matter.
Researchers say understanding these brain “eras” could help identify when the brain is most vulnerable to disruption and shed light on the timing of mental health and neurological disorders.
