Elsevier

The Lancet

Volume 379, Issue 9826, 28 April–4 May 2012, Pages 1630-1640
The Lancet

Series
Adolescence: a foundation for future health

https://doi.org/10.1016/S0140-6736(12)60072-5Get rights and content

Summary

Adolescence is a life phase in which the opportunities for health are great and future patterns of adult health are established. Health in adolescence is the result of interactions between prenatal and early childhood development and the specific biological and social-role changes that accompany puberty, shaped by social determinants and risk and protective factors that affect the uptake of health-related behaviours. The shape of adolescence is rapidly changing—the age of onset of puberty is decreasing and the age at which mature social roles are achieved is rising. New understandings of the diverse and dynamic effects on adolescent health include insights into the effects of puberty and brain development, together with social media. A focus on adolescence is central to the success of many public health agendas, including the Millennium Development Goals aiming to reduce child and maternal mortality and HIV/AIDS, and the more recent emphases on mental health, injuries, and non-communicable diseases. Greater attention to adolescence is needed within each of these public health domains if global health targets are to be met. Strategies that place the adolescent years centre stage—rather than focusing only on specific health agendas—provide important opportunities to improve health, both in adolescence and later in life.

Introduction

The present generation of people aged 10–24 years is the largest in history—with a population of 1·8 billion,1 they comprise a quarter of the world's population. Nearly 90% live in low-income and middle-income countries where they constitute a far greater proportion of the population than in high-income countries because of higher fertility rates (figure 1). The growth in adolescent populations coincides with a reduction in infectious disease, malnutrition, and mortality in infancy and early childhood, shifting attention to sexual and reproductive health, substance misuse, mental health, injury, obesity, and chronic physical illness, which become prominent during adolescence and need very different responses.3, 4

Many countries have entered a demographic transition in which falling fertility and longer, healthier life expectancy increase the proportion of people able to work. A healthy, educated workforce has the potential to shape a country's economic prospects.5 Conversely, poverty, inadequate education, mass unemployment, migration, natural disasters, and war result in social environments that can devastate the health of young people.6, 7, 8, 9, 10, 11

Young people were at the forefront of the social unrest across north Africa and the Middle East that began in Tunisia in December, 2010. Although many succeeded in toppling the restrictive regimes that they fought against, they faced serious threats to their lives and health. Such engagement is a powerful reminder that, by stark contrast with younger children, adolescents have an increasing capacity to be active agents of change within their communities.11, 12 It raises concerns about the extent of young people's exposure to violence, exploitation, and abuse, and suggests the need for greater protection of human rights.13

Many of the economic, educational, and political issues that affect young people are interlinked. Investment in education of adolescents has clear benefits to individuals and their health, but is also a strategy for enhancing employment, human rights, social capital, and community wealth.5 The adverse effects of child marriage and pregnancy at a young age (<18 years) on the health and human rights of girls is well appreciated, but just as potent is the dislocating effect of early pregnancy on girls' education, skill development, and social networks, which all undermine their present and future health and wellbeing, the health of their children, and their nations' social and economic prospects.14, 15

Key messages

  • At 1·8 billion, young people aged 10–24 years comprise more than a quarter of the world's population.

  • The health of adolescents has improved far less than that of younger children over the past 50 years.

  • The present generation of young people will take a different path through adolescence from previous generations and will face new challenges to their health and wellbeing. How they negotiate these years will have a powerful effect on their future health and their countries' economic and social prospects.

  • Biological aspects of puberty mark the start of adolescence, and key social-role transitions have historically signalled the end, which is now less distinct than in the past. Neurocognitive development is another element of biological maturation with major effects on decision making, emotional wellbeing, and behaviour.

  • A life-course perspective emphasises that the health of adolescents is affected by early childhood development and the biological and social-role changes that accompany puberty, shaped by social determinants of health that affect the uptake of health-related behaviours. The onset of these behaviours and states in adolescence affect the burden of disease in adults and the health and development of their children.

  • Social determinants that negatively contribute to adolescent health are structural (such as poverty and sex inequality) and proximal (such as intrafamilial violence, parental mental disorder, and substance misuse). These determinants often cluster within individuals. Protective effects are important targets for preventive interventions.

  • The ubiquitous nature of social media has changed the speed at which sociocultural norms are affected, with both risks and opportunities.

  • Adolescents can be powerful agents of personal change and community development.

  • Adolescents should be more prominent within future global public health policies and programming.

Societies typically define adolescence in terms of age and social roles with little consistency between countries. We focus on adolescents and young adults aged 10–24 years (referred to as young people and youth and hereafter referred to as adolescents) because this age-group encompasses most individuals who are going through the biological changes and social-role transitions that historically defined adolescence (panel). Although the biological sequences of puberty are highly consistent (table 1), changes in the timing of puberty, the nature of social-role changes, and the hopes and aspirations of adolescents across the world are widely affected by economic and sociocultural factors.

We assess the role of adolescence as a foundation for future health, emphasising the changing context of health and social development from late childhood to early adulthood and the place of adolescents within global public health. Our report is arranged around a conceptual framework that we have developed to describe the many factors affecting adolescent health and to put into context the subsequent reports in this Series (figure 2).

Section snippets

Adolescence within the life course

Social disadvantage and negative experiences in infancy and early childhood interfere with the achievement of normal developmental milestones in later childhood, such as healthy peer relationships and literacy.21 This can lead to peer rejection, school disengagement, academic failure, and early uptake of risky behaviours in adolescence.21, 22, 23 Adoption of a life-course perspective promotes the understanding that factors affecting preconception and early childhood can cumulatively affect

Puberty and social-role transitions

The onset of puberty has long been accepted as the starting point of adolescence, and key social-role transitions such as completion of education, employment, marriage, and childrearing historically signalled the end. Until the industrial revolution in the 1800s, the achievement of physical maturity generally paralleled social-role maturity.36 Even until the early 20th century, the delay between physical and social-role maturity was very short.

The decreasing age of onset of puberty that took

The biology of adolescent development

Like early childhood, adolescence is a sensitive period in which both normative and maladaptive patterns shape future trajectories. Part of this sensitivity relates to the social embedding of health risks and the biological changes before, during, and beyond adolescence.

100 years ago, puberty was widely thought merely a process of physical maturation that propelled individuals into different social contexts that affected their health.42 We now appreciate that puberty is a highly programmed and

The effects of social context on health

Both structural determinants of health (eg, national wealth and income inequality, access to education and health-care services, employment opportunities, and sex inequality) and proximal or intermediate determinants of health (eg, connectedness of adolescents to family and school) affect health-related behaviours and states in adolescence.61 Whereas many social determinants contribute to an individual's health across their lifetime, some have particular salience during adolescence. Social

Changes in the adolescent burden of disease

Changes in the biological and social transitions that define adolescence have important links to health (figure 2), although the processes by which this happens are complex and still not wholly understood. For example, the timing of puberty is linked to the onset of sexual activity and the risks of teenage pregnancy and sexually transmitted infections.73 That adult roles and responsibilities are now achieved at an older age in many high-income countries also has implications for sexual health,

Emerging drivers of adolescent health

In addition to the well established influences of parents and peers during adolescence, various new drivers are emerging. Marketing of unhealthy products and lifestyles (eg, tobacco, alcohol, and foods high in fat, sugar, and salt) clearly targets young people. Analogous to an infectious disease epidemic, mass media can be viewed as a vector that carries attitudes and products to an increasing number of hosts, resulting in outbreaks of previously uncommon behaviours. The extent of such

Adolescents and global health agendas

The Millennium Development Goals have driven global health policy for the past decade. Adolescence has become an important focus because improvement of adolescent health is central to the achievement of worldwide targets associated with maternal health, child mortality, and HIV/AIDS. The Millennium Development Goals continue to provide a very important opportunity to focus on sexual and reproductive health, which are fundamental to improvement of young people's health—maternal mortality is one

Recognition of adolescent health

Within child health, decades of clinical experience have stimulated research that has in turn affected national and global public policy, public health, and models of clinical practice within key domains of interest (eg, infant mortality and pneumonia). These efforts have contributed to the growth and integration of child public health. Collaborations, networks, advocacy, and funding organisations that stretch beyond health have resulted in national and worldwide investment and initiatives that

Embrace adolescence within the life course

What happens during adolescence is central to many emerging global health agendas. In view of this prominence, these agendas are unlikely to be successful without a greater focus on adolescence. Even when the contribution of adolescents to the wider agenda is indisputable, such as in international HIV/AIDS initiatives, it is often overlooked in terms of policy and programming. To rectify this omission, much greater appreciation of the importance of adolescence within a life-course perspective

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