Adolescence may not last forever but has been extended in the United Kingdom as child psychologists redefine maturity from 18 years of age to 25.

Informed by modern neuroscience, experts in the field of child psychology this week issued guidance, directing clinicians to reconsider how they view patients in younger adulthood, in an effort to ensure that late adolescence, early adulthood does not mean a gap in health and education. The evolution of thought on the issue of human maturation in psychology follows recent scientific findings regarding emotional maturity, hormonal development, and — most tellingly — neurological activity.

“The idea that suddenly at 18 you’re an adult just doesn’t quite ring true,” Laverne Antrobus, a child psychologist at London’s Tavistock Clinic, told the BBC. “My experience of young people is that they still need quite a considerable amount of support and help beyond that age.”

Rather than rushing a pronouncement on a youngster’s maturity, Antrobus said clinicians and members of the public should instead gain an appreciation for the development that occurs in those early adulthood years.

"Neuroscience has made these massive advances where we now don't think that things just stop at a certain age, that actually there's evidence of brain development well into early twenties and that actually the time at which things stop is much later than we first thought," Antrobus said.

Now, child psychologists such as Antrobus argue that adolescence comprises three stages, including an early period of 12-14 years of age, a middle period of 15-17 years of age, and “late adolescence” from 18 years of age to 25. Years of neurological research have shown human cognitive development to continue into the time period traditionally defined as early adulthood, as emotional maturity, self-image, and judgment evolve along with changes in the prefrontal cortex.

Simultaneously, hormonal activity typically associated with the teenage years continues well into the early 20s, according to Antrobus.

"A number of children and young people I encounter between the age of 16 and 18, the flurry of hormonal activity in them is so great that to imagine that's going to settle down by the time they get to 18 really is a misconception," Antrobus said.

However, the guidance from Antrobus and like-minded colleagues was destined to meet criticism from more conservative-minded academics, in addition to many people of a certain age. Frank Furedi, a sociologist at the University of Kent, told the BBC that Western culture has infantilized young adults in ways leading to a growing number of men and women in their 20s still living at home with their parents.

"Often it's claimed it's for economic reasons, but actually it's not really for that," Furedi said. "There is a loss of the aspiration for independence and striking out on your own. When I went to university it would have been a social death to have been seen with your parents, whereas now it's the norm.”

Other commentators with a conservative bent, however, note that economic hardships during a time of economic stagnation and government austerity might be managed without coddling youth. Rather, young men and women in “late adolescence” might live at home for financial reasons while still emerging as independent adults, contributing to bills, sharing household chores, and otherwise assuming greater responsibility as an autonomous agent in society.