A person has an “adolescent brain” until the age of 32, a Cambridge study has found.
Analysis of brain images from more than 3,800 people discovered five “major epochs” in the brain’s structure and workings which are marked by clear turning points.
The brain undergoes major changes at nine, 32, 66 and 83, it found.
Dr Alexa Mousley, who authored the study, said: “This study is the first to identify major phases of brain wiring across a human lifespan.
“These eras provide important context for what our brains might be best at, or more vulnerable to, at different stages of our lives.
“It could help us understand why some brains develop differently at key points in life, whether it be learning difficulties in childhood, or dementia in our later years.”
The human brain changes from “childhood” to “adolescent” at the age of nine, which is about the time of puberty, and the first years of life see the brain grow and refine its web of neurons in a process called “network consolidation”.
During the adolescent era the brain is at its peak for quick communication and is refining its organisation and growing its white matter. Grey matter processes information, and white matter sends it around the brain.
“Our findings suggest that in Western countries (i.e., the United Kingdom and United States of America), adolescent topological development extends to around 32 years old, before brain networks begin a new trajectory of topological development,” the scientists wrote in their paper.
At the age of 32 the brain then undergoes the single biggest change of a person’s lifetime.
The scientists said the adult brain forming at 32 is an average and it could happen up to three years earlier or later, depending on the person, with some people’s brains reaching adulthood at 35 and others at 29.
The “adult brain” period lasts the longest at an average duration of 34 years and spans the majority of a person’s working career.
The brain stabilises during this time and results in a plateau in intelligence and personality.
“Early ageing” happens at 66 and “late ageing” is the final form at 83.
The brain’s early ageing turning point coincides with the age of the state pension in the UK and the late ageing epoch happens roughly around the average life expectancy of a Briton.
Changes at this point are less significant than the developments at nine and 32, the scientists said, and instead are characterised by a subtle reorganisation and reduced connectivity. This is probably due to ageing causing white matter to degenerate, they said.
“This is an age when people face increased risk for a variety of health conditions that can affect the brain, such as hypertension,” the study said.
It is a common belief a person’s frontal lobe reaches full development at 25, and that this is a key point in a person becoming more mature.
This erroneous claim spread via social media and holds little scientific validity.
Prof Duncan Astle, the senior author of the new Cambridge study, said this study focused on connectivity, such as how well the frontal lobe is integrated with the rest of the brain.
“Our key finding is that at 32, on average, a person’s brain enters a new phase of change.” he told The Telegraph.
“That is, their brain continues to change, but in different ways that it did up to that point. Our point is not to say ‘this is when your brain has stopped changing’, but rather this is when your brain enters a new era of change.”
The study has been published in Nature Communications.