Adolescent Health. Adolescent Development

The definition of adolescence is variable; differing sources include those aged as young as 10 to as old as 24 years. The World Health Organization (WHO) defines adolescents as those aged 10 to 19years, youth 15 to 24years, and young people 10 to 24 years. Over 1.2 billion in number, adoles­cents make up 20% of the world’s population.

Although their absolute number continues to rise, their proportion of the world’s population is expected to fall over the next 20 years due to declining fertility rates. Over 85% of ado­lescents live in developing countries; in many sub-Saharan countries where the population is among the youngest in the world, the median age is between 15 and 16 years old. As a result, the vast majority of population growth in young people is expected to take place in developing countries (Figures 1 and 2).

Figure 1. Population of youth aged 10–24 in millions, stratified by regional economic development, 2007 and 2030. Reproduced from U.S. Census Bureau (2007) International Data Base. Washington, DC: US Census Bureau. http://www.census.gov/ipc/www/idb/

Figure 2. Population of youth aged 10–24 in millions, stratified by region, 2007 and 2030. Reproduced from U.S. Census Bureau (2007) International Data Base. Washington, DC: US Census Bureau. http://www.census.gov/ipc/www/idb/

Until recently, communicable diseases were the major causes of adolescent mortality and morbidity. Due to advances in health care and changes in the global eco­nomic and political milieu, social and behavioral pro­blems are the sources of most adolescent illness.

According to Blum and Nelson-Mmari (2004), the lead­ing causes of death in 15- to 29-year-olds worldwide in descending order are: unintentional injuries, HIV/AIDS, other infectious causes, intentional injuries/violence, and suicide (maternal mortality was not included in cal­culations). Nearly 2 million adolescents die annually from mostly preventable and treatable causes including accidental injuries, suicide, and homicide, making them a critical population for public health intervention.

Moreover, the quality of adolescent health is an impor­tant determinant of adult well-being. Many behaviors developed during adolescence, such as sexual activity or tobacco use, are continued into later life, impacting adult morbidity and mortality. WHO estimates that 70% of premature deaths in adulthood are caused by behaviors started during adolescence. Investing in adolescent health is important for the advancement not only of young people, but for their families, their communities, and society at large.

Adolescent Development.Similar to other periods in childhood, adolescence is a time marked by rapid development. Young people acquire an increasing sense of autonomy, individuality, and responsibility as they cognitively and emotionally transition to adulthood. The brain continues to mature until age 24, organizing by creating and pruning neural connections.

The onset of puberty also brings about dra­matic changes in a young person’s body. While most teens advance through predictable stages of development, adoles­cents are a heterogeneous population with great variance between individuals regarding their level of maturity, even among those of the same age.

During this time of increasing responsibilities and pressures, adolescents generally lack the developmental capacities and life skills, as well as social and financial resources, of mature adults. This paradox makes adolescents vulnerable to outside pressures, which for some youth potentiates poor decision making and, as a result, common health and behavioral problems such as substance use and early sexual activity.

Adolescence is typically divided into three stages, reflecting changing abilities, priorities, and developmental tasks over time. During early adolescence, ages 10 to 14, puberty begins. These children begin to appear more like adults due to the development of secondary sexual char­acteristics such as breasts or facial hair and the growth spurt.

A mature appearance may cause unwanted sexual attention or behavioral expectations unfit for their devel­opmental level. Most girls begin to menstruate and are physically able to have a family on their own, despite lacking the resources and life skills to do so. Young adolescents generally start to have romantic interests in others, although their relationships tend to be short-lived and relatively superficial.

These children think in con­crete terms, and so their behavior is based on societal guidelines, such as school or peer rules, instead of by their own code of ethics. They tend to have difficulties associating risks with consequences, and are the most optimistic about the future.

Physical maturation continues during middle adoles­cence, ages 14 to 17. While romantic relationships are more serious, they remain experimental and even exploit­ive, as this group becomes more influenced by their peers.

This group tends to question societal rules as they develop their own moral code and think in abstract terms more effectively. During late adolescence, 17 to 24years of age, many youth face serious decisions regarding their future career and establishing independent adult identities. Their romantic relationships often reflect an emerging maturity and intimacy and generally last for longer periods of time.

Ambivalence, conflict, and exploration are common and normal during this time of transition and self-reflection. A supportive environment made up of family, community, and society is critical during this vulnerable period to provide the best health outcomes for adolescents.