Scientists have mapped five major phases of human brain development, finding that the brain does not fully enter its “adult” mode until around the age of 32.
The study, which analysed brain scans from nearly 4,000 people aged from infancy to 90, identified four key turning points in brain structure at roughly ages 9, 32, 66 and 83. These turning points divide life into five distinct brain “eras”: childhood, adolescence, adulthood, early ageing and late ageing.
From birth to about age nine, the brain focuses on consolidating networks by trimming unused neural connections while strengthening active ones. During adolescence, which lasts on average until age 32, white matter grows and brain communication becomes more efficient, supporting improved cognitive performance.
The most significant shift happens in the early 30s, when the brain moves into its adult phase. This period is marked by greater stability in brain organisation and increased compartmentalisation of brain regions, and can last for more than three decades.
Around age 66, the brain enters an early ageing phase, followed by a late ageing stage beginning in the early 80s. These later phases are linked to declining connectivity and gradual degeneration of white matter.
Researchers say the findings could help identify when the brain is most vulnerable to disruption and may improve understanding of mental health conditions, which often emerge during adolescence.
