Scientists give new definition of when adulthood actually begins - it's later than you think

For decades now, much of the world has had a very clear idea of when adulthood actually begins, and that is 18 years old.

Yes, you may still be a teenager, but, at least in the UK, you're also able to legally vote, buy alcohol and tobacco, get a tattoo, serve on a jury, and enter into contracts, among other rights.

At this milestone age, you're also able to make major life decisions such as buying a house, getting married without parental consent, and joining the military or police force. You can also work full-time and be tried as an adult in court.

However, a piece of pop psychology has been floating around for some time now stating that our prefrontal cortex - AKA the part of your brain that controls executive functions like planning, decision-making, problem-solving, and emotional regulation - only develops a whole seven years later at 25. But, it's important to note, this little catchphrase is allegedly a myth.

But now, scientists have given a whole new definition of when adulthood actually begins - and it's way later than you think!

Neuroscientists at the University of Cambridge have just shared a new definition of when adulthood actually starts (Yuichiro Chino / Getty Images)

Earlier this week (25 November), neuroscientists at the University of Cambridge in England revealed they had identified four major 'turning points' in a person’s neurological development that extend well into adulthood.

The findings challenge conventional understanding of when our brains finish maturing.

"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 researcher Dr. Alexa Mousley, told the BBC, noting that this process can happen at different ages for different people.

Mousley's study, which was published in Nature Communications, identifies childhood as lasting until age nine, characterised by network consolidation where synapses are pruned and reorganised.

Following this, adolescence extends into the early thirties, marked by continued white matter growth and increasingly sophisticated organisation of the brain's communication pathways.

This adolescent period represents one of the most significant transformations the brain experiences across a person's lifetime, with the timing varying between individuals.

"Around the age of 32, we see the most directional changes in wiring and the largest overall shift in trajectory, compared to all the other turning points," Mousley explained, per the release.

"While puberty offers a clear start, the end of adolescence is much harder to pin down scientifically," she added. "Based purely on neural architecture, we found that adolescent-like changes in brain structure end around the early thirties."

According to the researchers, the brain only reaches adulthood at age 32 (Olena Malik / Getty Images)

Beyond age 32, the brain transitions into its adult phase, which is the most extended period of neurological development. This stage features stable brain architecture with minimal dramatic shifts in cognitive function or personality characteristics.

This plateau continues until age 66, marking the onset of early ageing. At this point, brain networks begin gradual restructuring, with declining connectivity as white matter deterioration begins, Mousley explained.

"This is an age when people face increased risk for a variety of health conditions that can affect the brain, such as hypertension," she added.

According to the experts, the final turning point of the brain happens at the age of 83, when a person enters what is known as the late ageing brain phase.

While the research noted that 'data is limited for this era', the researchers said that in this final period, 'brain connectivity declines even further, with increased reliance on certain regions'.

"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," senior author Prof. Duncan Astle, Professor of Neuroinformatics at Cambridge, added in the release, outlining that this information will be able to help scientists better understand the brain's journey during the course of a human life, and why it works the way it does.

"Understanding that the brain’s structural journey is not a question of steady progression, but rather one of a few major turning points, will help us identify when and how its wiring is vulnerable to disruption," he said.

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