New study finds adolescence continues into our 30s as brain development follows five key phases
A new study reveals adolescence continues far longer than once believed, reshaping how we view human development.
A major study mapping how the human brain changes across the lifespan has found that adolescence extends far beyond the teenage years and continues well into our early thirties. The research, conducted by scientists at the University of Cambridge, identifies five distinct phases of brain development, each marked by significant shifts in how the brain’s connections reorganise and function.
The findings challenge long-held assumptions about when adolescence ends, offering a clearer picture of the brain’s progression from childhood to late ageing. According to BBC News, the research team analysed around 4,000 brain scans from people aged up to 90 to trace how connections between brain cells change over time.
Their results show that adolescence spans from the age of nine to 32, marking it as the longest developmental stage before adulthood.
What phases does the brain go through?
The study outlines five clear phases: childhood, adolescence, adulthood, early ageing and late ageing. These stages were identified through patterns seen in the brain’s dynamic network of connections, which continually strengthen and weaken in response to learning and experience. Although individuals may reach these turning points at slightly different ages, the researchers were struck by how consistently these age markers appeared across the large dataset.
The research, published in Nature Communications, was able to identify these patterns due to the significant volume of scans available. The study illustrates how the brain does not follow a smooth, gradual path from birth to old age, but instead moves through distinct and measurable phases.
What defines the adolescent brain?
Adolescence begins at around nine-years-old, coinciding with the onset of major hormonal and developmental changes. During this period, the brain undergoes a dramatic shift towards efficiency. The neural network, which during childhood behaves like a freely wandering path, now becomes more direct and purposeful.
This phase marks the brain’s only period in which its network becomes more efficient rather than less. It is also when the risk of mental health disorders is at its highest. While adolescence has traditionally been linked to the teenage years, and more recently extended into the 20s, this study indicates it continues until the age of 32.
Dr Alexa Mousley, lead author of the study, highlighted that this prolonged phase aligns with many recognised measures of brain performance, which tend to peak in the early thirties. She noted the significance of adolescence lasting from nine to 32, describing it as a substantial and continuous developmental stage.
What happens after adolescence?
Once the brain reaches the age of 32, it enters adulthood – the longest and most stable phase, lasting until around 66. During this time, changes become slower, and the efficiency gained during adolescence begins to gently reverse. Dr Mousley said this phase corresponds with a plateau in intelligence and personality that many people recognise in their own lives.
From 66 onwards, the brain transitions into early ageing. This is not a sudden decline but a reorganisation, as different regions begin to work more independently rather than as one unified whole. This shift mirrors the age at which health concerns such as dementia and high blood pressure often start to appear.
Late ageing begins at around 83, although less data was available for this group. The patterns seen are similar to early ageing, though more pronounced. The researchers noted that recruiting healthy participants in this age range for brain scans was more challenging.
How do these findings connect to health and behaviour?
The study did not examine differences between men and women, leaving questions such as the impact of menopause for future research. However, experts say the findings offer important insights into how brain wiring relates to behaviour, cognitive abilities and vulnerability to conditions such as dementia or mental health disorders.
Professor Duncan Astle, part of the research team, noted that many neurological and developmental conditions are linked to the way the brain is wired. Differences in connectivity can influence attention, language, memory and a wide range of behaviours.
Prof Tara Spires-Jones of the University of Edinburgh, who was not involved in the research, described it as a “very cool study”, adding that the results align with what is already known about brain ageing. She cautioned, however, that not everyone will experience these changes at the same ages.
Why do these age milestones matter?
Dr Mousley said she was surprised by how closely the identified age phases aligned with major life events, from puberty to health changes in later life and even the social transitions that often occur in the early thirties, such as parenthood.
The research provides a clearer framework for understanding how the brain evolves throughout life. By showing that adolescence continues into our thirties, the study offers a new perspective on personal development, health risks and the ways our experiences shape us across the decades.
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