The world now has more young people than ever before – of the 7.2 billion people worldwide, over 3 billion are younger than 25 years, making up 42% of the world population. Around 1.2 billion of these young people are adolescents aged between 10 and 19 years.

Adolescence is a critical time of life. It is a time when people become independent individuals, forge new relationships, develop social skills and learn behaviours that will last the rest of their lives. It can also be one of the most challenging periods.

Adolescent health is starting to attract the attention it deserves, and is increasingly prominent in global health initiatives. This includes the Global Strategy for Women’s, Children’s and Adolescents’ Health, areas such as mental health (young people’s mental health is the theme of 2018’s World Mental Health Day on 10 October) and management of sexually transmitted infections (growing rates of infections in adolescents was much discussed at the 2018 International AIDS conference in Amsterdam).

Yet, a comprehensive approach to adolescent health is often lacking, with this critical age group very much at risk of being left behind in the development agenda. “For a long time there has been an assumption – sustained by critical gaps in data - that adolescents are healthy. Most of them indeed are, but much less so than we used to think. Data show that the considerable gains from investments in maternal and child health programmes are not sustained in adolescence: the reduction in child mortality was not mirrored by a similar reduction in adolescent deaths,” says Dr Princess Nothemba (Nono) Simelela, WHO’s Assistant Director-General for Family, Women, Children and Adolescents.

“Youth are central partners and collaborators because of their inherent strength to create change. WHO remains committed to meaningfully engage youth in our work and to implement youth lens in our planning and actions,” says Ms Diah Saminarsih, WHO’s Advisor on Gender and Youth.

In 2017, WHO and other UN partners launched a major initiative called Accelerated Action for the Health of Adolescents (AA-HA!) to change the way countries tackle adolescent health. The AA-HA! guidance calls for a systematic inclusion of adolescents’ expectations and perspectives in health planning processes.

“With this guidance, we wanted countries to have an AA-HA! moment - not only as in, ‘aha, now I know what the problem is’, but also as in, ‘aha, now I know what the solution is’,” explains Dr Valentina Baltag, at the Department of Maternal, Newborn, Child and Adolescent Health, at WHO, who helped develop the guidance. “The guidance is not only about facts and figures to show where to invest, but is also a compilation of the most up-to-date, tangible information from research and practice on what works.”

Partners such as UNICEF, UNAIDS and UNFPA were critical in developing the guidance. “Health is made at home and is a result of many sectors' direct or indirect interventions,” says Dr Stefan Peterson, Chief of Health at UNICEF. “The AA-HA! guidance sets out a broad approach to addressing the various aspects of adolescent health, helping governments to design comprehensive responses that meet the needs of adolescents and their communities,” he says.

Peterson says that UNICEF is prioritizing adolescents now because “Two decades of multisectoral investment are needed to produce a healthy, educated young adult. If we only focus on the first five years of a child’s life, adolescents end up falling through the cracks. Investing in adolescent health is key to unlocking lifelong health, productivity and national prosperity.”

A new WHO report on youth, health and development launched this week articulates how adolescent global and national leadership could be institutionalized and actively supported in WHO’s work with Member States and a diverse range of partners, including groups led by young people, to embed engagement with young people in every aspect of the health ecosystem.

The report refers to young people as a “powerhouse of human potential” and describes strategic opportunities to meaningfully engage them in transforming health and sustainable development. Young people can be critical agents of change, it says, if they are allowed to be part of the conversation in a fundamental way.

“With over 40% of the world’s population under the age of 24 years, young people have to be part of any meaningful solution to the world’s challenges—and this is their right. Ensuring young people’s meaningful, safe and effective engagement for health and sustainable development is a matter of urgency for Member States, WHO and partners, and young people themselves,” says Dr Shyama Kuruvilla, in WHO’s department for Family, Women’s and Children’s Health.

As boys and girls enter adolescence, health risks become increasingly skewed along gender lines. Some of the differences are biological, such as complications from teenage pregnancy or being at risk of being infected with human papillomavirus (HPV) that can lead to cervical cancer later in life - but many are shaped by societal gender norms such as expectations on girls to get married or on boys to earn an income at an early age.

Violence is one of the biggest threats that young people face – and much of this violence happens between peers. In the past year alone, one billion children worldwide – over half of all young people aged 2–17 years – have experienced emotional, physical or sexual violence. Both boys and girls experience high levels of violence, and policies developed need to be appropriate for the types of violence faced. 40% of 13-15 year olds were involved in a physical fight in the past 12 months.

Violence has a strong gender component: one in five girls under the age of 20 report experiencing sexual violence, compared to 8% of boys. Girls are more likely to experience sexual or physical violence from partners, or be forced into child marriage, trafficking, child labour, or genital mutilation.

Boys are more likely to be both victims and perpetrators of homicide, involving weapons such as firearms and knives: homicide is among the top five causes of death in adolescents, and males comprise over 80% of victims and perpetrators. Boys are also more likely to be in road traffic accidents, which can cost them their lives.

Social and economic inequalities always have a detrimental effect on health, and nowhere is this more apparent than with young people. Adolescents from ethnic minorities, refugees, young offenders, people who identify as LGBTQIA+, may face greater health challenges, including mental health problems, disabilities, or autism spectrum disorders, in part due to stigma, social exclusion, discrimination and rejection by their family or community.

“Social norms affect young people, whether they are rich or poor. A classic example is attitudes to menstruation in India, which can lead to the ostracization of girls from educational or social activities with lifelong repercussions, and barriers to fact-based sexuality education (especially for girls) in a number of countries,” says Dr Venkatraman Chandra-Mouli, Reproductive and Sexual Health Specialist at WHO.

Adolescence is a highly formative time for future health. While many of the challenges that emerge at this age are rooted in experiences in the womb or in young childhood, effects of the neurobiological changes in the very early years can emerge in adolescence. This will influence behaviours that can lead to heart disease and other chronic conditions that also tend to be established at this crucial time of life, including levels of physical activity, nutrition, tobacco smoking, and alcohol use. Most smokers start smoking when they are teenagers – one in two people who start and who continue to smoke will be killed by tobacco-related illnesses. Risky behaviours can begin as experiments but then become lifelong habits, with profound implications for health and well-being.

The impact of such health issues can affect not only current youth, but also future generations. If young people are exposed to violence, they are in turn more likely to perpetuate it themselves. Meanwhile, mental health issues that develop in adolescence can affect the way people later parent their own children, incurring potential consequences for generations to come.

“Half of mental health disorders arise before the age of 14,” explains Dr Tarun Dua, mental health expert at WHO. “If these are left untreated, they extend into adult life, thus impacting educational attainment, employment, relationships or even parenting.”

Self-harm is the third leading cause of deaths in 15-19 year olds. 80% of depression begins in adolescence, but many cases go undetected and untreated.

Moreover, many unhealthy behaviours and health conditions are interlinked. For instance, bullying can lead to self-harm, eating disorders, or anxiety disorders that can persist throughout their lifetime, as well as making it more likely that a young person will have suicidal thoughts.

The converse can also be true, however. Although this period of life can be fraught with difficulty, there is also an enormous opportunity to protect future health. Often for the first time, young people will be making independent decisions about what to eat and how much, whether to do regular sports and exercise, whether to engage in safe or unsafe sexual practices, or whether or not to try addictive substances such as drugs or alcohol. 

Thus, positive development is critical for young people, in particular learning specific social skills, being able to form bonds with other people, developing a sense of self-worth, gaining a sense of right and wrong, and building the ability to empathise with others.

“Some adolescents will make healthy choices but some will start making unhealthy choices. These may start as experimental behaviours, but without adequate support can become lifelong habits. The challenge for us is to design policies that will make healthy choices easy, and unhealthy choices difficult, expensive and inaccessible,” says Baltag.

When young people are protected by age-appropriate policies and programmes, and given safe spaces in which to not only survive but actually thrive, they can develop resilience that ensures they grow into healthy, well-adjusted adults. Effective interventions at this time, will therefore yield lifelong benefits and longlasting returns. 

A particular challenge in addressing risks that young people face is that prohibitive approaches (e.g. laws restricting the sale of alcohol and tobacco use) do not always work without adequate family and societal support and protection. The widespread availability of pornography coupled with a lack of adequate sex education in many countries can mean that young people are not aware of risks they may face, or understand healthy sexual behaviour. Education (both at home and at school) is critical in teaching young people how to behave responsibly.

“Sexuality education is about much more than talking to young people about sex and condoms, but rather aims to prepare young people for a healthy, and a pleasurable sexual and reproductive life,” explains Chandra-Mouli. “There is ample evidence from countries around the world that well-designed, well-delivered sexuality education programmes do good and do not result in harm, that they improve knowledge and understanding, promote positive behaviours and when combined with a healthy dose of gender, actually reduce health problems such as unwanted pregnancies and sexually transmitted infections.”

Young people navigate almost every element of their lives, especially their social lives, through technology. While it can sometimes lead to obsessive behaviours such as internet or gaming addiction, technology can also be a way to provide them with such critical information, connect them with services or empower them in their own healthcare. For example, digital health programmes about sexual health, physical activity or diet; or providing adolescents the ability to provide confidential online feedback to health providers on their experience with care.

Many of the health challenges that young people face – noncommunicable diseases, violence, road traffic accidents – are set to rise as the world continues to become more crowded, more urban, and more mobile. Increasing exposure to tobacco, drugs and alcohol via the internet and the media, and ever-increasing marketing of unhealthy products to young people, is ensuring that young people continue to be at risk of obesity or alcohol or substance abuse at a time when they are most vulnerable, and when their bodies are still in crucial phases of development. The need to invest in the health of adolescents has become urgent.

“Investing in the health and well-being of adolescents, especially adolescent girls, should be a top priority for national and international policymakers. These investments are not only the right thing to do, they also yield tremendous economic and social returns and are vital to achieving the global sustainable development agenda,” says Dr Natalia Kanem, Executive Director, UNFPA.

WHO’s AA-HA! guidance aims to support countries to improve adolescent health. Many countries have inadequate insight of the main causes of adolescent health issues or causes of death. AA-HA! supports countries in mapping the health needs of their adolescents, and brings together evidence-based policies to show what works.

The partnership that was created while developing this guidance sets the stage for a new era in global adolescent health. Coordinated by WHO, it was developed with the active participation of United Nations agencies, civil society organizations, academics, governments, and, most importantly, young people themselves.

And now it is paying off. In every country where the AA-HA! guidance has been used, coalitions of UN partners, nongovernmental organizations, community groups and young people have been formed to steer national action. “In the past, agencies and programmes tended to work in isolation, each looking after a particular health issue that affects adolescents – for instance, HIV, pregnancy or anaemia. Now we hope the focus will change from the diseases to the adolescent - the person, in the entirety of her or his needs,” explains Baltag. 

In just over a year, teams from 68 countries have been trained in applying the AA-HA! guidance for national priority-setting, programming, monitoring and evaluation, and 18 countries are in the process of using the AA-HA! approach to update national strategies and policies.

“The AA-HA! strategy is a critical step in the right direction. It supports countries to advance the respect, protection and promotion of the right to health of adolescents, especially for those who are the most marginalized from society and face high levels of inequality, discrimination, exclusion and violence, which jeopardizes their access to services and health outcomes,” says Mr Tim Martineau, acting Deputy Executive Director, Programme Branch at UNAIDS.

Alongside efforts to strengthen adolescent health in a holistic manner, a number of key commitments have been made in specific areas. One example is preventing unintended and unwanted pregnancy through improving access to and use of contraception. Recognizing the benefits of preventing adolescent pregnancy both for the health of adolescent girls, and for the population as a whole, a number of countries have included bold commitments to step up efforts and financing for adolescent contraception at the Family Planning Summit in London in 2017.

In tackling adolescent health challenges, building resilience is key. For mental health conditions, for example, resilience comes from having emotional, psychological and social support such as strong peer networks, being able to speak openly to adults at school or at home, but also being physically healthy through a good diet, physical activity, and sleeping well. “Interventions that can impact multiple health issues at the same time are essential, such as life skills training for mental health, drug and alcohol abuse and violence prevention,” says Dr Berit Kieselbach, violence prevention expert at WHO.

It is also a time to proactively engage young people in measures that promote positive attitudes to sexuality and sexual health across genders, while ensuring youth are protecting themselves against chronic diseases in the future. Early adolescence is the critical period for vaccination of young girls against HPV, the leading cause of cervical cancer cases. When given before young people become sexually active, the HPV vaccination provides an immense opportunity to reduce the burden of cervical cancer later in life.

Tackling gender norms that have a negative effect on health is critical. Studies of gender norms shows that during adolescence, in many countries, boys see an expansion of their horizons – they gain access to new opportunities, whereas girls can have fewer options, and their worlds shrink. At the same time, boys also are put at risk through the reinforcement of negative gender stereotypes, which encourage risk-taking behaviours and can perpetuate violence. Engaging young people in conversations about their own perceptions of gender norms, promoting gender equity in parenting and education, and tapping into the reach of media and technology could all help counter harmful gender norms that begin from infancy.

Both girls and boys require support in overcoming barriers to accessing healthcare. In Nepal, for example, the Ministry of Health realized its adolescent sexual and reproductive health programme did not account for barriers such as distance and cost of travel, inability to come during opening hours, and a lack of privacy and confidentiality. It is now planning to introduce measures to address such constraints, including an increased focus on outreach services in disadvantaged areas and enhanced community engagement.

A push to improve primary health care, led by the Global Conference on Primary Health Care in Astana this October, is an opportunity to shape primary care services that are responsive to adolescents’ needs, including through youth engagement. Such a system would need to ensure that: adolescents know when and where to access services and pay no fees at the point of care; that providers are trained and have incentives for delivering adolescent-responsive care, including preventive care; and that no mandatory third party authorizations (e.g. parental or guardian permissions) are required for adolescents to use sexual and reproductive health services.

At the same time, while it will be important both to strengthen the ability of existing health services to respond to adolescents’ health needs, it will also be important to reach young people where they are. This might include new uses of technology, as well as programmes that support active youth outreach at homes and schools. 

An initiative led by WHO and the United Nations Educational, Scientific and Cultural Organization (UNESCO) aims to make every school a ‘health-promoting school’. The two organizations are working to develop and promote a set of global standards to guide schools and their communities to become healthy and safe places for learning.