Scientists have identified five major phases of human brain development, revealing that the brain doesn’t settle into its “adult” mode until the early 30s.
The findings come from a large study analysing brain scans from nearly 4,000 people ranging from infancy to 90 years old. Researchers found that brain development follows five broad “epochs,” separated by major transitional turning points at around ages nine, 32, 66 and 83.
According to the study, the five phases are:
- Childhood: birth to around age 9
- Adolescence: roughly ages 9 to 32
- Adulthood: beginning around age 32 and lasting into the mid-60s
- Early ageing: starting around age 66
- Late ageing: beginning around age 83
During childhood, brains undergo heavy “pruning,” where unused connections are removed and frequently used ones are reinforced. Although this makes the brain more specialised, the overall efficiency of wiring decreases during this phase. Grey and white matter grow rapidly, and brain folding and thickness reach their peak.
In the adolescent era, white matter continues to grow and brain networks become more efficient and refined, which is linked to improving cognitive performance and reasoning abilities.
The most significant shift occurs around age 32, when the brain transitions into a more stable adult pattern. During this long phase, brain structure becomes more compartmentalised and intelligence and personality tend to plateau. Researchers suggest major life events like parenthood may influence brain changes during this period.
From the mid-60s onward, brain connectivity begins to decline as part of the ageing process, with more pronounced changes after the early 80s due to degeneration of white matter.
Researchers say understanding these developmental “turning points” could help identify when the brain is most vulnerable to mental health conditions and neurological disorders.
