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Adolescent Physical and Social Development
See also Part XV and Chapters 577 and 578 .
During the preteen, teenage, and young adult years, young people undergo not only dramatic changes in physical appearance, but also rapid changes in physiologic, psychological, and social functioning. Hormonally driven physiologic changes and ongoing neurologic development occur in the setting of social structures that foster the transition from childhood to adulthood. This period of development comprises adolescence , which is divided into 3 phases—early, middle, and late adolescence—each marked by a characteristic set of biologic, cognitive, and psychosocial milestones ( Table 132.1 ). Although individual variations in the timing and pace of development undoubtedly exist, these changes follow a fairly predictable pattern of occurrence. Gender and culture profoundly affect the developmental course, as do physical, social, and environmental influences. Given the interaction of these domains, a biopsychosocial perspective is best suited to approach the healthcare of the adolescent.
Table 132.1
Milestones in Early, Middle, and Late Adolescent Development
| VARIABLE | EARLY ADOLESCENCE | MIDDLE ADOLESCENCE | LATE ADOLESCENCE |
|---|---|---|---|
| Approximate age range | 10-13 yr | 14-17 yr | 18-21 yr |
| Sexual maturity rating * | 1-2 | 3-5 | 5 |
| Physical | Females: secondary sex characteristics (breast, pubic, axillary hair), start of growth spurt Males: testicular enlargement, start of genital growth |
Females: peak growth velocity, menarche (if not already attained) Males: growth spurt, secondary sex characteristics, nocturnal emissions, facial and body hair, voice changes Change in body composition Acne |
Physical maturation slows Increased lean muscle mass in males |
| Cognitive and moral | Concrete operations Egocentricity Unable to perceive long-term outcome of current decisions Follow rules to avoid punishment |
Emergence of abstract thought (formal operations) May perceive future implications, but may not apply in decision-making Strong emotions may drive decision-making Sense of invulnerability Growing ability to see others' perspectives |
Future-oriented with sense of perspective Idealism Able to think things through independently Improved impulse control Improved assessment of risk vs reward Able to distinguish law from morality |
| Self-concept/identity formation | Preoccupied with changing body Self-consciousness about appearance and attractiveness |
Concern with attractiveness Increasing introspection |
More stable body image Attractiveness may still be of concern Consolidation of identity |
| Family | Increased need for privacy Exploration of boundaries of dependence vs independence |
Conflicts over control and independence Struggle for greater autonomy Increased separation from parents |
Emotional and physical separation from family Increased autonomy Reestablishment of “adult” relationship with parents |
| Peers | Same-sex peer affiliations | Intense peer group involvement Preoccupation with peer culture Conformity |
Peer group and values recede in importance |
| Sexual | Increased interest in sexual anatomy Anxieties and questions about pubertal changes Limited capacity for intimacy |
Testing ability to attract partner Initiation of relationships and sexual activity Exploration of sexual identity |
Consolidation of sexual identity Focus on intimacy and formation of stable relationships Planning for future and commitment |
* See text and Figs. 132.1 and 132.2 .
Physical Development
Puberty is the biologic transition from childhood to adulthood. Pubertal changes include the appearance of the secondary sexual characteristics, increase in height, change in body composition, and development of reproductive capacity. Adrenal production of androgen, mainly dehydroepiandrosterone sulfate (DHEAS), may occur as early as 6 yr of age, with development of underarm odor and faint genital hair ( adrenarche ). Maturation of the gonadotropin-releasing hormone (GnRH) pulse generator is among the earliest neuroendocrine changes associated with the onset of puberty. Under the influence of GnRH, the pituitary gland secretes luteinizing hormone (LH) and follicle-stimulating hormone (FSH); initially this occurs in a pulsatile fashion primarily during sleep, but this diurnal variation diminishes throughout puberty. LH and FSH stimulate corresponding increases in gonadal androgens and estrogens. The triggers for these changes are incompletely understood but may be mediated in part by the hormone leptin, high concentrations of which are associated with increased body fat and earlier onset of puberty. Both genetic and environmental (epigenetic) contributions to the regulation of pubertal timing are likely.
Sexual Development
The progression of the development of the secondary sex characteristics may be described using the sexual maturity rating (SMR) scale (ranging from 1, preadolescence, to 5, sexual maturity), or Tanner stages . Figs. 132.1 and 132.2 depict the physical findings of breast and pubic hair maturation at each SMR ( Tables 132.2 and 132.3 ). Although the ages at which individual pubertal changes occur may vary, the timing and sequence of these changes relative to one another is predictable ( Figs. 132.3 and 132.4 ). The wide range of normal progress through sexual maturation is affected by genetics, the psychosocial environment, nutrition, and overall health status. Environmental exposures may play a role as well.
Table 132.2
Sexual Maturity Rating (SMR) Stages in Females
From Tanner JM: Growth at adolescence, ed 2, Oxford, England, 1962, Blackwell Scientific.
| SMR STAGE | PUBIC HAIR | BREASTS |
|---|---|---|
| 1 | Preadolescent | Preadolescent |
| 2 | Sparse, lightly pigmented, straight, medial border of labia | Breast and papilla elevated as small mound; diameter of areola increased |
| 3 | Darker, beginning to curl, increased amount | Breast and areola enlarged, no contour separation |
| 4 | Coarse, curly, abundant, but less than in adult | Areola and papilla form secondary mound |
| 5 | Adult feminine triangle, spread to medial surface of thighs | Mature, nipple projects, areola part of general breast contour |
Table 132.3
Sexual Maturity Rating (SMR) Stages in Males
From Tanner JM: Growth at adolescence, ed 2, Oxford, England, 1962, Blackwell Scientific.
| SMR STAGE | PUBIC HAIR | PENIS | TESTES |
|---|---|---|---|
| 1 | None | Preadolescent | Preadolescent |
| 2 | Scant, long, slightly pigmented | Minimal change/enlargement | Enlarged scrotum, pink, texture altered |
| 3 | Darker, starting to curl, small amount | Lengthens | Larger |
| 4 | Resembles adult type, but less quantity; coarse, curly | Larger; glans and breadth increase in size | Larger, scrotum dark |
| 5 | Adult distribution, spread to medial surface of thighs | Adult size | Adult size |
In males the first visible sign of puberty and the hallmark of SMR 2 is testicular enlargement, beginning as early as 9.5 yr, followed by the development of pubic hair. This is followed by penile growth during SMR 3. Peak growth occurs when testis volumes reach approximately 9-10 cm 3 during SMR 4. Under the influence of LH and testosterone, the seminiferous tubules, epididymis, seminal vesicles, and prostate enlarge. Sperm may be found in the urine by SMR 3; nocturnal emissions may be noted at this time as well. Some degree of breast tissue growth, typically bilateral, occurs in 40–65% of males during SMR 2-4 as a presumed consequence of a relative excess of estrogenic stimulation. This usually resolves with ongoing maturation.
In females , typically the first visible sign of puberty and the hallmark of SMR 2 is the appearance of breast buds ( thelarche ), between 7 and 12 yr of age. A significant minority of females develops pubic hair ( pubarche ) prior to thelarche. Less visible changes include enlargement of the ovaries, uterus, labia, and clitoris and thickening of the endometrium and vaginal mucosa. A clear vaginal discharge may be present before menarche (physiologic leukorrhea). Menses typically begins within 3 yr of thelarche, during SMR 3-4 (average age 12.5 yr; normal range 9-15 yr) (see Fig. 132.4 ). The timing of menarche is determined largely by genetics; contributing factors likely include adiposity, chronic illness, nutritional status, and the physical and psychosocial environment. Early menstrual cycles often are anovulatory and thus somewhat irregular, but typically occur every 21-45 days and include 3-7 days of bleeding, even during the 1st year following menarche.
The onset of puberty and menarche appear to be occurring at earlier ages than previously reported in the United States. Several studies from 1948–1981 identified the average age for the onset of breast development as ranging from 10.6-11.2 yr of age. Multiple reports since 1997 suggest a significantly earlier average age of onset, ranging from 8.9-9.5 yr in black females to 10.0-10.4 yr in white females. Almost 25% of black females and 10% of white females initiate breast development by 7 yr of age. Early breast development may be associated with a slower tempo of puberty (i.e., longer time to menarche). There also appears to be a trend toward decreasing ages for the onset of pubic hair development and menarche. Data from the National Health and Nutrition Examination Survey (NHANES), a nationally representative, longitudinal survey in the United States, show a decline in the average age of menarche of 4.9 mo between the 1960s and 2002. Changes in the timing of menarche within ethnic groups, however, were significantly smaller. The larger change seen in the population as a whole may be partially explained by changes in the ethnic makeup of the sample. The reasons for the larger decrease in age for breast development have been postulated to include the epidemic of childhood obesity as well as exposure to estrogen-like environmental toxins (endocrine disruptors), but further research in this area is needed.
Although fewer data are available on changes in the timing of puberty in males, they appear to be experiencing a similar trend. Although the method of assessing the onset of puberty (i.e., inspection vs. palpation of the testes) varies between studies, it appears that the average age for the onset of genital and pubic hair development may have decreased by 1-2 yr over the past several decades in many industrialized countries. Evidence for an association of obesity with the timing of puberty in males has been inconsistent.
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