Scientists have identified five major phases of human brain development, with key “turning points” occurring around the ages of nine, 32, 66 and 83, according to a large new study.
The research, based on brain scans from nearly 4,000 people aged from infancy to 90, found that brain development does not follow a smooth, steady path. Instead, it progresses through distinct “epochs” marked by shifts in how neural connections are organised.
The five brain eras identified were:
- Childhood – from birth to around age 9
- Adolescence – from about 9 to 32
- Adulthood – beginning around age 32 and lasting more than 30 years
- Early ageing – starting at around age 66
- Late ageing – beginning around age 83
Researchers measured brain structure using 12 different indicators, including efficiency of neural wiring, how organised networks are, and how strongly the brain relies on central “hub” regions.
During childhood, the brain undergoes heavy “pruning”, where unnecessary neural connections are removed and frequently used ones are strengthened. Grey and white matter grow rapidly, and the brain’s outer folding becomes more stable.
The adolescent phase is marked by continued growth in white matter and steadily improving efficiency of communication between brain regions, which is linked to better cognitive performance. This is also the period when many mental health disorders tend to emerge.
The biggest structural shift happens around age 32, when the brain enters its adult phase and stabilises. Networks become more compartmentalised, and intelligence and personality typically level off, according to previous research.
From the mid-60s onwards, connectivity gradually declines, largely due to age-related changes in white matter, with further shifts occurring after age 83.
Researchers say understanding these turning points could help identify when the brain is most vulnerable to disruption and disease.
