Study finds four major turning points in brain growth at ages 9, 32, 66, and 83
A new study suggests that human adolescence may extend up to the age of 32. According to researchers, the brain undergoes four major developmental shifts around ages 9, 32, 66, and 83. The findings were published Tuesday in the journal Nature Communications, based on the analysis of nearly 4,000 brain scans of individuals up to 90 years old.
Researchers say the analysis identifies five distinct “stages” of the human brain — childhood, adolescence, adulthood, pre-old age, and old age. According to them, personality and intelligence stabilize only after adolescence ends — around age 32.
When Do the Changes Occur?
The study found that ages 9, 32, 66, and 83 are the four most important milestones in brain development. These ages mark transitions related to adolescence, personality stabilization, reorganization, and decline.
Childhood: Birth to Age 9
During this phase, grey matter and white matter grow rapidly. Johns Hopkins Medicine in the US notes that grey matter is responsible for information processing, while white matter supports signal transmission. Researchers say early life is crucial for synapse formation and elimination, as well as the expansion of grey and white matter.
Adolescence: Ages 9 to 32
Previously, adolescence was thought to begin in early teens and end before the age of 20. But researchers now argue that while the onset is clear, the end is not. Social and cultural factors influence this extended stage. In Western countries, the brain remains in this phase until around age 32. During this time, white-matter structures grow rapidly, and the brain shows the highest degree of directional change.
Adulthood: Ages 32 to 66
This long stage is marked by slower, steady development. Major structural changes are minimal, and personality and intelligence reach stability.
Pre-Old Age: Ages 66 to 83
During this period, white matter begins to weaken. Different regions of the brain start working more independently, reducing coordination. Some people begin to experience conditions such as dementia or high blood pressure.
Old Age: Age 83 and Beyond
Although data is limited, researchers say brain connectivity continues to decline. The link between age and brain structure becomes weaker.
Why Is This Study Important?
One of the most significant findings is the expanded understanding of how long adolescence lasts. While the World Health Organization defines adolescence as ages 10 to 19, a 2018 report in The Lancet suggested that adolescence may extend well into the 20s. The new study sheds more light on the vulnerabilities, risks, and complex brain changes during this prolonged adolescent phase.
Professor Duncan Astle of the University of Cambridge says that looking back, people can see their lives progressing through different phases — and the brain appears to pass through similar phases as well.
