Adolescence lasts until 24, scientists say

Anyone between the ages of 10 and 24 should be considered adolescent, according to a new paper published in The Lancet.

Writing in the medical journal’s Child and Adolescent Health publication, doctors from the Royal Victoria Hospital in Melbourne argue that the biological and social development associated with the transition to adulthood now takes far longer than in past generations.

The average age of the onset of puberty has been steadily dropping in the developed world for decades, due to improvements in health and nutrition. In the UK, the average girl has her first period at the age of 12, compared to 14 or older in past centuries.

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At the other end of the spectrum, young people are leaving home, marrying and having children at later ages than their predecessors, the BBC reports, leaving them in a prolonged state of “semi-dependency”.

A realistic understanding of this transitional time “is essential for developmentally appropriate framing of laws, social policies, and service systems”, the paper’s authors argue.

There is also a biological underpinning for a broader definition of adolescence. Neuroscientists now know that, even after visible signs of puberty have disappeared, the brain continues to change and mature until a person reaches their mid-20s or even later, CNN reports.

In 2013, child psychologists in the UK were issued new guidance instructing them to treat patients up to the age of 25, rather than the previous cut-off of 18.

“The idea that suddenly at 18 you're an adult just doesn't quite ring true,” child psychologist Laverne Antrobus from London's Tavistock Clinic told the BBC at the time.

“My experience of young people is that they still need quite a considerable amount of support and help beyond that age.”

Predictably, millennials welcomed the news that they had a few more years of “semi-dependency”: