Scientists have identified five major phases of human brain development after analysing brain scans from nearly 4,000 people ranging from infancy to age 90.
The research found that the brain goes through four major “turning points” at roughly ages 9, 32, 66 and 83, creating five distinct developmental eras rather than a slow, steady progression. Researchers say these shifts mark changes in how the brain’s wiring is organised and how efficiently different regions communicate.
The five brain eras identified are:
- Childhood (birth to ~9 years)
- Adolescence (~9 to ~32 years)
- Adulthood (~32 to ~66 years)
- Early ageing (~66 to ~83 years)
- Late ageing (83+ years)
From birth to age nine, the brain undergoes “network consolidation,” where excess neural connections are trimmed while stronger ones remain. During adolescence, white matter continues to grow and brain networks become more efficient, supporting improved cognitive abilities.
The biggest structural shift in brain organisation happens around age 32, when the brain enters its longest and most stable “adult” phase. From this point, brain architecture becomes more compartmentalised and development plateaus compared with earlier years.
Later in life, at around 66 and again at 83, brain connectivity begins to decline, likely due to ageing and gradual degeneration of white matter.
Researchers say the findings could help explain why certain mental health conditions often appear in adolescence and may help identify periods when the brain is most vulnerable to disruption.
