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Introduction and overview
Cytotherapy ( IF 3.7 ) Pub Date : 2017-11-01 , DOI: 10.1016/j.jcyt.2017.08.005 Massimo Dominici 1 , Nan Zhang 2 , A John Barrett 2
Cytotherapy ( IF 3.7 ) Pub Date : 2017-11-01 , DOI: 10.1016/j.jcyt.2017.08.005 Massimo Dominici 1 , Nan Zhang 2 , A John Barrett 2
Affiliation
The period of adolescence encompasses the transition from childhood to adulthood during the second decade of life. It is one of the most crucial periods in an individual’s life, because during adolescence many key social, economic, biological, and demographic events occur that set the stage for adult life. Until age ten, most children in the developing world live at home, go to school, have not yet gone through puberty, and are unmarried. By age 20, most have left school and home and have become sexually active, and a large proportion has married. The quality of their future lives depends largely on the extent to which adolescents take advantage of opportunities for personal growth by going to school and being employed while avoiding potentially problematic outcomes of sexual relations, such as early dropout from school, unplanned pregnancy, or adverse health effects. In the developing world as a whole, the 1995 population of adolescents aged 10–19 is estimated at 914 million, about one-fifth of the population of all ages (see Table 1). The proportion of adolescents varies modestly among regions, from a high of 23 percent in Africa to 19 percent in Asia. The number of adolescents aged 10–19 has grown rapidly in recent decades in all regions of the developing world, but the proportion of the population aged 10–19 has declined slightly from 22 percent in 1975 to 20 percent in 1995. This trend is primarily the result of rapid fertility declines that have taken place since the 1960s and that subsequently reduced the growth rate of the number of adolescents in many developing countries. According to the median population projection of the United Nations, the number of adolescents is expected to reach 1.13 billion by the year 2025—an increase of 219 million or 24 percent. The most rapid future growth is expected to occur in Africa and the slowest in Asia and Latin America—the two regions that have experienced the earliest and most rapid declines in fertility in recent decades. The articles in this special issue of Studies in Family Planning summarize available evidence concerning reproductive behavior among adolescents in the developing world, analyze its causes and consequences, and initiate a debate on how best to design policies and programs to address the urgent needs of adolescents. Before a discussion of the significance of the research in this volume, a brief overview of research findings on the timing and prevalence of key demographic events and experiences affecting adolescents is provided below.
更新日期：2017-11-01
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