Scientists have identified five major phases of human brain development, with key “turning points” typically occurring around the ages of 9, 32, 66 and 83, according to a large new study.
The research, which analysed brain scans from nearly 4,000 people ranging from infancy to age 90, shows that brain development does not progress in a smooth, steady line. Instead, it shifts through distinct eras, each with different patterns of neural organisation.
The five brain “epochs” are:
- Childhood (birth to about age 9) – marked by rapid growth, pruning of unused synapses and changes in brain wiring
- Adolescence (around 9 to early 30s) – increased efficiency of brain connections and refining of communication networks
- Adulthood (from about 32 to mid-60s) – the longest and most stable phase, where brain structure largely plateaus
- Early ageing (around 66 onward) – the beginning of gradual declines in connectivity
- Late ageing (around 83 onward) – more pronounced reductions in brain network efficiency
The strongest shift in brain wiring happens in the early 30s, when the brain moves into what researchers describe as its “adult” operating mode. During this time, the brain becomes more compartmentalised and stable compared to earlier periods of rapid change.
Researchers say these findings could help pinpoint when the brain is most vulnerable to disruption, including the period of adolescence when many mental health conditions first appear.
In later life, the study found that declining connectivity is likely linked to age-related white matter degeneration, helping explain changes in cognitive function as people grow older.
