According to a new paper, young people continuing their education for longer, as well as delayed marriage and parenthood, has pushed back popular perceptions of when adulthood begins.

Adolescence now lasts from the ages of 10 to 24, although it used to be thought to end at 19, according to a new paper published in the Lancet Child & Adolescent Health Journal.

These findings are based on the fact that people are reaching "adult" milestones at a much later age than they used to.

According to the Office of National Statistics in Britain, the average age for a man to enter their first marriage in 2013 was 32.5 years and 30.6 years for women across England and Wales. This represented an increase of almost eight years since 1973.

Some scholars and healthcare professionals have argued that this new understanding of adolescence should be reflected in policy.

Lead author Professor Susan Sawyer, director of the centre for adolescent health at the Royal Children's Hospital in Melbourne, writes: "Although many adult legal privileges start at age 18 years, the adoption of adult roles and responsibilities generally occurs later."

She says delayed partnering, parenting and economic independence means the "semi-dependency" that characterises adolescence has expanded.

“Arguably, the transition period from childhood to adulthood now occupies a greater portion of the life course than ever before at a time when unprecedented social forces, including marketing and digital media, are affecting health and wellbeing across these years.”

The call for redefinition is an attempt to ensure health policy safeguards the future health of the 1.8 billion people currently aged between 10-24.

Some existing international laws and policies seem to already take this extended version of adolescence into account. In the US, for example, the Affordable Care Act allows people to stay on their parents’ health insurance until 26 (until Trump manages to screw that up, that is.) Other laws reflect the vast confusion concerning what society deems to be the age of responsible – in the States, people get their driver’s license at 16, but can’t rent a car until age 25.

The paper has been met with some criticism that is in encouraging the infantilization of young people, including young adults.

But Prof Russell Viner, president-elect of the Royal College of Paediatrics & Child Health disagrees with these assessments, and says that broadening adolescence can be seen as "empowering young people by recognising their differences".

"As long as we do this from a position of recognising young people's strengths and the potential of their development, rather than being focused on the problems of the adolescent period."