Adolescence now lasts from the ages of 10 to 24, although it used to be thought to end at 19, scientists say.

　　科学家说，青春期现在可以从10岁持续到24岁，尽管过去一直被认为以19岁为结束。

　　Young people continuing their education for longer, as well as delayed marriage and parenthood, has pushed back popular perceptions of when adulthood begins.

　　年轻人继续接受教育的时间越来越长，而晚婚晚育也使得人们对成年何时开始的普遍看法一扫而空。

　　Changing the definition is vital to ensure laws stay appropriate, they write in an opinion piece in the Lancet Child & Adolescent Health journal.

　　改变定义对于确保法律保持适当至关重要，他们在《柳叶刀儿童与青少年健康》杂志的评论中写道。

　　But another expert warns doing so risks "further infantilising young people".

　　但另一位专家则警告说，这样做有可能导致“年轻人进一步无所事事”。

　　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.

　　被称为下丘脑的大脑部分开始释放激活身体的垂体和性腺的激素，被认为是青春期的开始。

　　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.

　　过去这种情况发生在14岁左右，但随着大部分发达国家健康和营养水平的提高，该年龄下降到10岁左右。

　　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.

　　因此，在英国这样的工业化国家，过去一百五十年来，女孩第一次月经的平均年龄已经下降了四年。

　　Half of all females now have their period by 12 or 13 years of age.

　　现在，所有女性中有一半的月经年龄开始在12或13岁之间。

　　There are also biological arguments for why the definition of adolescence should be extended, including that the body continues to develop.

　　对于青春期的定义应该延续的原因，还有生物学的观点，包括身体在不断发展。

　　For example, the brain continues to mature beyond the age of 20, working faster and more efficiently.

　　例如，大脑在20岁以后继续成熟，工作更快更高效。

　　And many people’s wisdom teeth don’t come through until the age of 25.

　　许多人的智齿直到二十五岁才会长出来。

　　Young people are also getting married and having children later.

　　年轻人也晚结婚并晚生孩子。

　　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.

　　根据国家统计局的统计，2013年，英格兰和威尔士男性平均婚龄为32.5岁，女性为30.6岁。这是自1973年以来近八年的增长。

　　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."

　　该研究主要作者墨尔本皇家儿童医院青少年健康中心主任苏珊·索耶教授写道：“尽管许多成人的法定特权从18岁开始，但成人角色和责任通常要往后。”

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

　　她表示，推迟婚姻，养育子女和经济独立意味着青春期的“半依赖”特征扩大了。

　　This social change, she says, needs to inform policy, such as by extending youth support services until the age of 25.

　　她说，这种社会变革需要调整政策，比如将青年支持服务延伸到25岁。

　　Age definitions are always arbitrary, she writes, but "our current definition of adolescence is overly restricted".

　　她写道：“年龄定义总是武断的，但是”我们目前对青春期的定义过于严格“。

　　"The ages of 10-24 years are a better fit with the development of adolescents nowadays."

　　“10-24岁的年龄更适合当今青少年的发展。”