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 Adolescence now lasts from the ages of 10 to 24, although it used to be thought to end at 19, scientists say. 
 
 Young people continuing their education for longer, as well as delayed marriage and parenthood, has pushed back popular perceptions of when adulthood begins. 
 
 Changing the definition is vital to ensure laws stay appropriate, they write in an opinion piece in the Lancet Child & Adolescent Health journal. 
 
 But another expert warns doing so risks "further infantilising young people". 
 
 When puberty begins 
 
 Puberty is considered to start when the part of the brain known as the hypothalamus starts releasing a hormone that activates the body's pituitary and gonadal glands. 
 
 This used to happen around the age of 14 but has dropped with improved health and nutrition in much of the developed world to around the age of 10. 
 
 As a consequence, in industrialised countries such as the UK the average age for a girl's first menstruation has dropped by four years in the past 150 years. 
 
 Half of all females now have their period by 12 or 13 years of age. 
 
 When the body stops developing 
 
 There are also biological arguments for why the definition of adolescence should be extended, including that the body continues to develop. 
 
 For example, the brain continues to mature beyond the age of 20, working faster and more efficiently. 
 
 And many people's wisdom teeth don't come through until the age of 25. 
 
 Delaying life's milestones 
 
 Young people are also getting married and having children later. 
 
 According to the Office of National Statistics, 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. 
 
 Lead author Prof 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. 
 
 Social policy 
 
 This social change, she says, needs to inform policy, such as by extending youth support services until the age of 25. 
 
 "Age definitions are always arbitrary", she writes, but "our current definition of adolescence is overly restricted". 
 
 "The ages of 10-24 years are a better fit with the development of adolescents nowadays." 
 
 Prof Russell Viner, president-elect of the Royal College of Paediatrics & Child Health, said: "In the UK, the average age for leaving home is now around 25 years for both men and women." 
 
 He supports extending the definition to cover adolescence up until the age of 24 and says a number of UK services already take this into account. 
 
 He said: "Statutory provision in England in terms of social care for care leavers and children with special educational needs now goes up to 24 years," as does provision of services for people with cystic fibrosis. 
 
 'Infantilising young people' 
 
 But Dr Jan Macvarish, a parenting sociologist at the University of Kent, says there is a danger in extending our concept of adolescence. 
 
 "Older children and young people are shaped far more significantly by society's expectations of them than by their intrinsic biological growth," she said. 
 
 "There is nothing inevitably infantilising about spending your early 20s in higher education or experimenting in the world of work." 
 
 And we should not risk "pathologising their desire for independence". 
 
 "Society should maintain the highest possible expectations of the next generation," Dr Macvarish said. 
 
 Prof Viner disagrees with Dr Macvarish's criticism and says 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." ||||| 
 
 Jonathan Forani, CTVNews.ca Staff 
 
 
 
 
 
 Growing up will take a little longer if a group of new scientists get their way. 
 
 In a new opinion piece in the Lancet Child & Adolescent Health journal, a group of seven academics make a case for redefining adolescence from ages 10-19 to 10-24. It is a redefinition, they say, that reflects an evolving society where puberty hits earlier, bodies develop into the 20s, and where young people leave home, get married, have children and gain economic independence later than ever. 
 
 “Adolescence encompasses elements of biological growth and major social role transitions, both of which have changed in the past century,” they write in the article, published Wednesday. 
 
 “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 aged 10-24 who make up more than a quarter of the world’s population, according to the United Nations Population Fund. 
 
 “An expanded and more inclusive definition of adolescence is essential for developmentally appropriate framing of laws, social policies, and service systems,” the new article reads. It’s not the first time lead author professor Susan Sawyer, director of the Centre for Adolescent Health at the Royal Children's Hospital in Melbourne has discussed redefining adolescence. In a 2012 study on the subject, she wrote that inconsistent age definitions only serve to compound the problem of addressing adolescent health concerns. Some information systems define people ages 15-19 as “adults,” which will “effective render adolescence invisible.” 
 
 .@LancetChildAdol Viewpoint: The age of #adolescence—an extended and more inclusive definition to framing better laws, social policies, and service systems for this life phase @LancetYouth https://t.co/KKpJeGjv4W pic.twitter.com/RfVRIDYovk — The Lancet (@TheLancet) January 18, 2018 
 
 “Good information systems are an important step towards making adolescents and their health more visible to policy makers, researchers, donors and development partners,” she wrote in 2012. Sawyer and her co-authors suggest a definition of adolescence across three age categories, 10-14 years, 15-19 years, and 20-24 years. That is how Statistics Canada defines young years, often further describing the 15-19 years as “adolescents” and the 20-24 years as “young adults.” 
 
 Some academics contest the Lancet piece, including sociologist Jan Macvarish from the University of Kent, who tweeted that “science really can't tell us how to live our lives and raise our children and what adulthood means.” 
 
 But Sawyer is intent on a redefinition. She found that much research on the adolescent years tends to focus on children under the age of five instead of the later years when minds and bodies continue to develop which she tweeted in November ahead of the new article’s release. 
 
 “Let’s make adolescents visible,” she wrote.
– Good news for young people tired of being told to grow up: A team of academics writing in the Lancet wants to expand the period in life we think of as adolescence by five years, CTV News reports. "The transition period from childhood to adulthood now occupies a greater portion of the life course than ever before," the team writes in an article published Wednesday. They argue for delaying the end of adolescence, which starts at 10 years old, from 19 years old to 24 years old. "Age definitions are always arbitrary, [but] our current definition of adolescence is overly restricted," the BBC quotes lead author Susan Sawyer as saying. The team argues there are physiological and sociological reasons for expanding adolescence. Scientists now know the brain continues to develop after the age of 20. And young people are moving away from their parents, getting married, and having their own children later than at any other point in history. In Britain, people are getting married nearly eight years later than they were in 1973. The team says adolescence should be redefined for the good of the 1.8 billion people between ages 10 and 24 on the planet. “An expanded and more inclusive definition of adolescence is essential for developmentally appropriate framing of laws, social policies, and service systems,” the article states. However, sociologist Jan Macvarish warns we could end up infantilizing young people. "Society should maintain the highest possible expectations of the next generation," she says.