People don’t become ‘adults’ until their 30s

You're an adult, but your brain might not be, experts say.You're legally an adult when you turn 18, in most of the United States. However, from a scientific perspective, adulthood is an unsolved mystery.

People do not become proper adults until they have entered their thirties, according to brain researchers who say hard definitions of adulthood are looking “increasingly absurd”.

While the UK judicial system currently recognises a person of 18 as a mature adult, scientists say people are undergoing significant changes to their brains for many years.

The latest research suggests these changes can have significant effects on young people’s behaviour, as well as making them more susceptible to mental health disorders.


Processes that involve boosting the conductivity of nerves, building neural networks and “pruning” away unwanted connections begin in the womb and continue for decades.

A burst of upheaval in the brain is thought to account for the notoriously difficult behaviour of adolescents, but does not necessarily end once people leave their teens.

“What we’re really saying is that to have a definition of when you move from childhood to adulthood looks increasingly absurd,” said professor Peter Jones, a neuroscientist at the University of Cambridge.

“It’s a much more nuanced transition that takes place over three decades. Systems like the education system, the health system and the legal system make it convenient for themselves by having definitions.”

However, he said these systems were adapting and despite the legal definition of adulthood, experienced judges recognised the difference between a 19-year-old defendant and a “hardened criminal” in his late thirties.

Professor Daniel Geschwind, from the University of California, stressed the degree of individual variability in brain development. He said for practical reasons, education systems mistakenly tended to focus on groups, rather than individuals.

The scientists also discussed the impact environment could have on psychotic conditions like schizophrenia.