People are not full adults until their 30s, scientists say

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.

These new insights have major implications for society, the scientists claim.

They were speaking ahead of a meeting of the Academy of Medical Sciences in Oxford, which focuses specifically on brain development.

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,” Professor Peter Jones, a neuroscientist at the University of Cambridge, told journalists at an event in London.

“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.

“There isn’t a childhood and then an adulthood. People are on a pathway, they’re on a trajectory,” Professor Jones said.

Professor Daniel Geschwind, from the University of California at Los Angeles, stressed the degree of individual variability in brain development.

He pointed out that 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, which arise from a complex interplay of genetic and outside influences.

Schizophrenia diagnosis is most common in teenagers and people in their early twenties, as once the brain has sorted out its circuits and finally “matured”, the risk of psychosis greatly diminishes.

Professor Jones said people living in cities, particularly poor and migrant populations, faced an increased risk of mental disorders thanks to a “potent cocktail” of environmental influences affecting developing brains.

Studies have shown that minority populations can be up to three times more likely to experience schizophrenia.

“Being a migrant isn’t specifically about one particular group, it’s about being a minority within a majority,” said Professor Jones.

“It’s probably to do with having to live constantly on the alert – I mean a low level of vigilance that minorities experience when they’re living in host communities.”

Additional reporting by PA