LAUSR

In much academic writing on matters of adolescent public health, age is treated as a proxy for developmental stage, and yet the two are very different concepts and this lack of distinction neglects important biological processes that impact the well-being of young people. Large-scale surveys of adolescents frequently describe differences in the health and risk behaviour, as well as a wide range of health measures, as related to age (Currie et al. 2008, 2012a). Between the ages of 11 and 15 years, adolescents are immersed in a complexity of changes to their physical selves, cognitive function, emotional range, impulsivity, desire for risk taking and hormonal function (Patton and Viner 2007). These changes affect their health-related behaviour, well-being, social and gender identity, social relations and ability to concentrate and learn. However, the timing and pace of pubertal development varies significantly between the sexes, and between individual girls and boys, depending on a wide range of personal, social and environmental factors (Walvoord 2010). Genetics also play a part as do biological determinants such as adiposity (Currie et al. 2012b), as well as environmental oestrogens and toxins from substances such as pesticides and other chemicals that they consume, inhale or are in contact with through their skin. The sensitivity of the adolescent body to environmental chemicals is as yet not well understood. Nevertheless, there is growing evidence that puberty is starting at younger ages with exposure to harmful environmental substances causing endocrine disruption, as one candidate explanation. The stage of puberty that individuals have reached at a particular age in the second decade of life is a key factor in their mental, physical and emotional well-being (Oldehinkel et al. 2011). At age 11 some girls may be well developed physically, with breast development and reproductive development well advanced. In the same classroom will be girls who, in contrast, still have the physical appearance of a child. At age 13 some boys are small in stature having not experienced a growth spurt, their voices are unbroken, and their faces hairless, while others have had a spurt in height, have developed a muscular physique, show signs of a moustache and have a deepened voice. These differences in appearance that puberty may imbue have an effect on how adolescents feel about themselves and how others, including the same and opposite sex peers and adults, such as parents and teachers, treat them (Williams and Currie 2000). Girls who reach puberty early are known to have a host of behavioural characteristics not observed in their age peers who are late developers. They are more likely to have early sex, to begin smoking and drinking, to be concerned about their body weight and to have mental health problems (Kaltiala-Heino et al. 2003; Patton et al. 2004). Early puberty is associated with mental health problems in middle adolescence. Some of these differences equalise by the later teenage years, but others persist through young and later adulthood and studies have shown detectable differences in social status, BMI, body image and mental well-being among women in their forties (Stattin and Magnusson 1990). Boys who mature early have some social and physical advantage over their later developing peers. They are more likely to be popular and excel at sports as well as have earlier romantic relationships. However, recent evidence suggests they also have detrimental psychological outcomes (Mendle and Ferrero 2012). Among the factors that contribute to earlier puberty are proximal social determinants related to family life. Girls growing up with no father at home, a stepfather at home or living with no parents, especially those in institutional care, have higher odds of early puberty (Steppan et al. under & Candace Currie [email protected]