In a fascinating study, British scientists have revealed that there are four pivotal ages for the brain, and that it goes through five distinct phases – with key turning points at ages nine, 32, 66 and 83, reports the BBC.
Around 4 000 people up to the age of 90 had scans to reveal the connections between their brain cells, and the University of Cambridge researchers said the results showed that the brain stays in the adolescent phase until our early 30s, when we “peak”.
They said the results could help us understand why the risk of mental health disorders and dementia varies through life.
The brain is constantly changing in response to new knowledge and experience – but the research shows this is not one smooth pattern from birth to death.
Instead, these are the five brain phases:
• Childhood – from birth to age nine
• Adolescence – from nine to 32
• Adulthood – from 32 to 66
• Early ageing – from 66 to 83
• Late ageing – from 83 onwards
“The brain rewires across the lifespan. It’s always strengthening and weakening connections, and it’s not one steady pattern: there are fluctuations and phases of brain rewiring,” lead author of the research Dr Alexa Mousley told the BBC.
Some people will reach these landmarks earlier or later than others, but the researchers said it was striking how clearly these ages stood out in the data.
These patterns have only now been revealed due to the quantity of brain scans available in the study, which was published in the journal Nature Communications.
The five brain phases
Childhood: The first period is when the brain is rapidly increasing in size but also thinning out the overabundance of connections between brain cells, called synapses, created at the start of life.
The brain gets less efficient during this stage. It works like a child meandering around a park, going wherever takes their fancy, rather than heading straight from A to B.
Adolescence: That changes abruptly from the age of nine when the connections in the brain go through a period of ruthless efficiency. “It’s a huge shift,” said Mousley, describing the most profound change between brain phases.
This is also the time when there is the greatest risk of mental health disorders beginning.
Unsurprisingly, adolescence starts around the onset of puberty, but this is the latest evidence suggesting it ends much later than we assumed. It was once thought to be confined to the teenage years, before neuroscience suggested it continued into your 20s and now early 30s.
This phase is the brain’s only period when its network of neurons gets more efficient. Mousely said this backs up many measures of brain function suggesting it peaks in your early 30s, but added it was “very interesting” that the brain stays in the same phase between nine and 32.
Adulthood: Next comes a period of stability for the brain as it enters its longest era, lasting three decades.
Change is slower during this time compared with the fireworks before, but here we see the improvements in brain efficiency flip into reverse.
Mousely said this “aligns with a plateau of intelligence and personality” that many of us will have witnessed or experienced.
Early ageing: This kicks in at 66, but it is not an abrupt and sudden decline. Instead there are shifts in the patterns of connections in the brain.
Instead of co-ordinating as one whole brain, the organ becomes increasingly separated into regions that work tightly together, like band members starting their own solo projects.
Although the study looked at healthy brains, this is also the age at which dementia and high blood pressure, which affects brain health, are starting to show.
Late ageing: Then, at the age of 83, we enter the final stage. There are less data than for the other groups as finding healthy brains to scan was more challenging. The brain changes are similar to early ageing, but even more pronounced.
Mousely said what really surprised her was “how well the different ages align with a lot of important milestones”, such as puberty, health concerns later in life, and even the pretty big social shifts in your early 30s such as parenthood.
‘A very cool study’
The study did not look at men and women separately, but there will be questions such as the impact of menopause.
Duncan Astle, Professor of Neuroinformatics at the University of Cambridge and part of the team responsible for the research, said: “Many neurodevelopmental, mental health and neurological conditions are linked to the way the brain is wired. Indeed, differences in brain wiring predict difficulties with attention, language, memory, and a whole host of different behaviours.”
The Director of the Centre for Discovery Brain Sciences at the University of Edinburgh, Prof Tara Spires-Jones, who did not work on the research paper, said: “This is a very cool study highlighting how much our brains change over our lifetimes.”
She said the results fit well with our understanding of brain ageing, but cautioned that not everyone will experience these network changes at exactly the same ages.
Study details
Topological turning points across the human lifespan
Alexa Mousley, Richard Bethlehem, Fang-Cheng Yeh & Duncan Astle.
Published in Nature Communications on 25 November 2025
Abstract
Structural topology develops non-linearly across the lifespan and is strongly related to cognitive trajectories. We gathered diffusion imaging from datasets with a collective age range of zero to 90 years old (N = 4,216). We analysed how 12 graph theory metrics of organisation change with age and projected these data into manifold spaces using Uniform Manifold Projection and Approximation. With these manifolds, we identified four major topological turning points across the lifespan – around nine, 32, 66, and 83 years old. These ages defined five major epochs of topological development, each with distinctive age-related changes in topology. These lifespan epochs each have a distinct direction of topological development and specific changes in the organizational properties driving the age-topology relationship. This study underscores the complex, non-linear nature of human development, with unique phases of topological maturation, which can only be illuminated with a multivariate, lifespan, population-level perspective.
Nature Communications article – Topological turning points across the human lifespan (Open access)
See more from MedicalBrief archives:
Adolescence ‘now lasts from ages 10-24’
Mental health disorders to affect half the world by 75 – large global study
Brain ageing in black people faster from midlife than for white people – US cohort study