Whether you subscribe to the idea of self-absorbed millennials often seen in today’s media, or that of a debt-burdened 'generation in crisis', what it means to be adolescent is hard to define. Ultimately it comes down to a mixture of social, biological, psychological, cultural and personal factors. Even the exact age range of 'adolescence' is in question – while the years between childhood and adulthood have traditionally been defined as being between 10-24 years of age, this is highly country and culture-dependent.

But the world's population of young people is the largest in modern history. The forces that shape our lives today will impact us into adulthood, and thus impact the society we live in. Adolescence is the time of our lives in which we take huge bounds: psychologically and biologically but also socially.

And how much of the adolescent experience is determined by external factors? The increasing prevalence of non-communicable diseases (NCDs) is linked to an obesogenic environment: one where soda and fast food are cheaper than healthy groceries, and in which urban development policies push public areas online rather than creating physical spaces in which to to run and play. Though NCDs have traditionally been thought of as diseases of adulthood, smoking, drinking, drug-taking, inactivity and obesity all start to appear in adolescence, and we are seeing a growing number of young people developing NCDs.

Meanwhile climate change and air pollution threaten to affect lung health in comparable rates to smoking, and reports show 'climate anxiety' is a real issue for many adolescents living in areas threatened by rising sea levels. In fact, half of the mental health disorders experienced in adulthood began in adolescence.

All this raises the question: are adolescents having their right to health upheld?

According to the World Health Organization, health is not simply the absence of disease, but rather is a state of complete physical, mental and social well-being. Taking a rights-based approach, adolescents' right to health is upheld by prioritising the maximum available resources to promote this wellbeing and for these resources to be allocated without discrimination. However, are current resources really being prioritised in this way?

As a global community we have spent the last century trying to address childhood health, and have more recently been focusing on the health of older adults. In doing so, we have forgotten to promote health at one of the most essential but also risky times of life: adolescence.

A report published recently in The Lancet described several barriers to adolescents accessing high-quality healthcare, categorised by availability, accessibility, acceptability and equity. Laws and policies can prevent certain groups of young people from accessing certain types of healthcare (for example, women accessing sexual health services), or by permitting healthcare that is negative in approach (such as gay conversion therapy). As well as these explicit examples of barriers to young people, there are also implicit barriers: health services that treat certain privileged groups more positively compared to other groups, such as homeless youth. The intersectionality between being young and being from a traditionally marginalized population puts adolescents at high risk of poor health. Health systems and policy already neglect both young people and marginalized groups. As such, the systematic discrimination one faces as a young person from a marginalized group is immense.

How can adolescents lead the way in improving their health and wellbeing?

What is the scope for change in the future? Perhaps the solution lies in foregrounding the voices of adolescents themselves. In Bamenda, the capital of a province in north-western Cameroon, 62% of the population are between 12 and 35 years old, with 13,000 of these people living with disabilities. Despite government efforts, this group faces discrimination and exclusion from participation in social and cultural life in Cameroon. But now a youth-led project is aiming to change the lives of these young people. The project uses social media campaigns to raise awareness about existing rights for those with disabilities. It also provides training on running a small business and accessing microfinance, helping to secure economic empowerment for young people with disabilities. Young people are taking matters into their own hands.

At Edinburgh University, a longstanding student-based campaign led the university to divest from all coal, oil and gas holdings, making it the largest UK university endowment fund to do so. This multi-million pound change in investment was thanks to the efforts of young people advocating for health and environmental concerns to be placed above financial interests.

And finally, it seems that engaging adolescents can improve health outcomes for treatment as well as prevention. Take the example of Isobel, a teenager with Type 1 diabetes who describes the difficulty of having to take responsibility for managing her condition when starting secondary school. By working alongside her healthcare providers to design an adolescent-focused approach, she describes feeling empowered to take control of her diabetes and to stay positive about her health needs. In this way, instead of shoehorning adolescent populations into pre-existing services, health services designed for and by adolescents allow young people to develop a positive relationship with their health.

What are the key messages for integrating an adolescent-focussed approach ?

Former UN secretary general Ban Ki-Moon has said that while “currently not thought of as central to sustainable development, and badly served by it, adolescents are being left behind”. However, steps can be taken to bring youth to the fore.

1. Adolescents are not just naive, inexperienced and unrealistic - and in fact are tired of being stereotyped as such. Adolescents are energised and activated, ready to take matters into our own hands, and in ways you may not have previously envisaged. A great example of this is the March For Our Lives movement. After countless high school shootings had no effect on gun legislation, this year’s attack on Marjory Stoneman Douglas High School in Florida, in which 17 students died, led adolescent survivors to organise a movement. These teenagers used their platform to take a stand against current gun control policies, which arguably remain at the whim of financial lobbies and party politics, and instead urged policymakers to prioritize the health and wellbeing of young people in the US. The youth-led march that followed was one of the largest in history, and the movement is now focusing on improving youth voter turnout at the polls.

2. Adolescents are specific about our goals. We are not just concerned with ideals of equity and sustainability; we have a vested interest in seeing these actualised. As a result, we are ready to make sure these ideas are specific, measurable, attainable, realistic and time-bound. We are not in the business of empty rhetoric; we realise we simply do not have the luxury.

3. Adolescents are ready to create a meaningful partnership with you. While we have our own ideas and take on the world around us, we also know we have a lot to learn and we are ready to listen – but trusting that we will be given a platform to be heard as well.

4. Adolescent engagement means complete engagement. Being young is hard enough, let alone being young and part of a marginalized group. If young people are to be involved and engaged, then this participation needs to be for all young people, not just the most privileged. We all deserve a seat at this table and are excited to pull up a chair next to you.

As Vittoria Tonin, an insightful young person herself, wrote in The Lancet: “Our health systems need to start listening to what we are saying and what we are asking for.”

It is a simple solution, but complex to implement: if we want our health systems and policy to promote health for young people, and ALL young people, they need to be included in the planning, designing and production of policy and practice.