In many ways, adolescence is the healthiest and most resilient period of the lifespan. Almost everything you can measure improves between childhood and adolescence--strength, speed, reaction time, reasoning abilities, immune function, increased resistance to cold, heat, hunger and dehydration and most types of injury. And yet, when we go from middle-school age to late adolescence to early adulthood, overall morbidity and mortality rates increase by 200 to 300 percent.
While these problems in adolescence have been recognized throughout human history, the critical questions remain: Are the changes based in biology? Are they based in the hormones of puberty? Are there specific brain changes that underpin some aspects of risk-taking, sensation-seeking and the emotional changes at puberty?
The modern study of adolescence really began in 1904 by G.S. Hall, who wrote of this period as a time of heightened "storm and stress." That term continued to influence many psychologists and developmentalists for a long period of time.
It was not until the 1960s and 1970s that anyone looked at the biologic underpinnings of adolescence. Even then, researchers and clinicians had only a narrow understanding of hormones and explained the problems of adolescence as due to "raging hormones." While this may be an oversimplification, there is strong empirical evidence for some aspects of the storm-and-stress metaphor during puberty.
First, there is increased conflict with parents. Adolescents are not necessarily more likely to argue, but the intensity of emotion is much higher, and conflicts are more likely to escalate to a higher state. Secondly, mood volatility increases. Thirdly, risk-taking, recklessness and sensation-seeking increase as adolescents seek experiences that evoke strong emotions and intense feelings.
Adolescence cannot be defined solely as the teenage years, nor can it be defined simply in biologic terms. It is really a suite of changes with relative synchrony, consisting of several component processes: It is a time of rapid physical growth and sexual maturation; a time when the secondary sexual characteristics that accompany becoming reproductively mature occur; a time of profound motivational and emotional changes; a time of much cognitive development in the sense of measuring cognitive abilities; a time when there is a maturation of judgment and self-regulation skills. And, there are brain changes linked to each component.
The interval lengthens
Research has shown that from 1860 to 1960 the age of menarche changed from about 15 1/2 years on average to about 13 years. An epidemiologic study of 17,000 girls in U.S. pediatric practices found that at age seven, 7 percent of the European-American girls and 27 percent of the African-American girls were already into the first stage of puberty. By eight years of age, the figures rose to 15 percent and 47 percent.
Therefore, when we think about adolescent brain changes, we're not just looking at the late teenage years. Some of these changes start occurring for a lot of kids by seven, eight, nine and 10 years of age.
The 2000 census found the average age of menarche was 12, and the average age of first marriage for females was 26. …