Age—not the whole story
Age is a convenient way to define adolescence.8 But it is only one characteristic that delineates this period of development.9 Age is often more appropriate for assessing and comparing biological changes (e.g. puberty), which are fairly universal, than the social transitions, which vary more with the socio-cultural environment.
The biological changes during adolescence do not all start at 10 years or stop at 20 years. Some important endocrine changes start before age 10—for example, the production of adrenal androgens—and some neurodevelopmental changes that take place during adolescence continue into the early twenties.10 Still, in general the most profound and rapid pubertal changes take place during the second decade.
Of course, a 10-year-old is very different from a 19-year-old. To accommodate the different phases of development in the second decade of life, adolescence is often divided into early (10–13 years), middle (14–16 years) and late (17–19 years) adolescence.11Stages Sawyer SM et al. Adolescence: a foundation for future health
In addition to age, other important variables are sex—adolescent girls tend to reach biologically defined developmental milestones up to two years ahead of adolescent boys—and gender, since expectations and societal norms differ significantly between adolescent boys and adolescent girls in most societies.Why focus
The proper functioning of one person is crucial for the society because our problems affect our behaviour, which will sooner or later affect the whole society.
trans, 12-14, Argentina
It is important because I want to live a long life, and I don't want to be restricted by any illness that would be the result of being unhealthy. I want to be a role model to children that I may have because I know how important it is to have someone that you can look up to and to motivate you to be healthy and to exercise.
female, 15-17, United Kingdom
Health is the basis for everything. If you want to study or work, you need to be in good physical and mental health.
female, 15-17, South Africa
Health is relative, based on the way you observe it. You can have a healthy body but an aching soul. I think it sums up to a balance of forces that make your body and mind work together to be able to experience freedom and with that, to create goals.
male, 15-17, Mexico
Your health is not only your future but also the future of those around you. If I were to die at a young age, I would be unable to contribute to the economy or the population. An individual contracting a disease increases the risk of other individuals within that community contracting it. Therefore, it is important to keep healthy to ensure my safety and the safety of others.
female, 15-17, Saudi Arabia
Health is life. Being in good health allows you to really throw yourself into life.
female, 15-17, France
Adolescents on the meaning of health: To have the ability to do things well, without any sort of discomfort or pain. To ensure a comfortable future, without any complications like diabetes or any sort of cardiac disease, etc., caused by what was done in the past.
Gender not specified, 18–19, Mexico
Health is important to me because being in a state of complete health means being able to function at my full potential, and hence being able to perform at my best and contribute as much as I can to the activities I am involved in.
female, 15-17, Switzerland
If you feel well, you produce, you contribute, you are happy and you create a positive social environment.
female, 18-19, Mexico