PUBERTY: AN INTEGRATED BIOSOCIAL PERSPECTIVE

The myriad molecular-biological, molar-psychological, and social changes that characterize
puberty engender scientific interests that span the biomedical, behavioral, and
social sciences. Hence, interdisciplinary perspectives necessarily are required to characterize
adolescent development (Lerner, 1998; Magnusson, 1999; Susman, 1997). Research
foci on pubertal development now include genetic and neuroendocrine mechanisms
that initiate puberty; influences from the molecular to the social contextual; the
significance of timing of puberty; and the dynamic interactive processes among physical
growth changes, emotions, problem behavior, cognition, and risky sexual activity
(but these latter studies remain relatively rare). Given the diversity and magnitude of pubertal
changes, an integrative theory is essential for understanding the fragmented findings
regarding pubertal development. This chapter presents a review of puberty as a
biopsychosocial transition that initiates psychological changes and that simultaneously
initiates changes in the social contexts in which adolescents find themselves. This theoretical
approach is referred to as dynamic integration and refers to the essential fusion
of processes across psychological, biological, and contextual levels of functioning.
The absence of an integrated biosocial perspective on puberty has historically been
problematic. Puberty as a biological event that deterministically modifies behavior was
derived from evolutionary (Parker, 2000) and psychodynamic (Freud, 1958; Hall, 1904)
theories that dominated the early 20th century. The perceptual salience of sexual maturation
was considered to heighten the psychological significance of biological pubertal
changes (Brooks-Gunn & Petersen, 1984). In the last three decades, behaviorism, contextualism,
and learning theory supplanted theories of development and evolution. Empirical
research came to reflect a dominant interest in contextual influences (e.g., peers
and schools) on development (e.g., Simmons & Blyth, 1987). Social contextualism gave
rise to the social constructionist viewpoint that the psychological significance of puberty
is derived from how others view puberty-related changes. Pubertal changes were
considered more graphic to others than to the adolescents themselves. The biologicaldeterministic
and social constructionist views of adolescence disregarded the dynamic
integration of biological, psychological, and contextual levels of analysis.
16 Puberty and Psychological Development
The integration of biological and psychological processes experienced a renaissance
with the publication of Petersen’s perspective on puberty and psychological development
(Petersen & Taylor, 1980). Shortly thereafter, the publication of Girls at Puberty
(Brooks-Gunn & Petersen, 1983) and a special issue of the Journal of Youth and Adolescence
on timing of puberty (Brooks-Gunn, Petersen, & Eichorn, 1985) brought to
scientific consciousness an integrated perspective that considered the multiple levels of
development. This emerging biopsychosocial perspective simultaneously began to be
articulated in theoretical models that focused on the centrality of interactions between
biological, psychological, and contextual processes (Lerner, 1987). Coincident with the
articulation of these biopsychosocial theories, empirical studies assessing the relationships
between physical growth and pubertal hormone levels and psychological development
began to appear in the literature. These studies addressed issues of family interaction
(Steinberg & Hill, 1978), adjustment (Nottelmann et al., 1987), aggressive behavior
(Susman et al., 1987), emotions (Brooks-Gunn & Warren, 1989) and sexuality (Udry,
Billy, & Morris, 1986; Udry, Billy, Morris, Groff, & Raj, 1985; Udry & Talbert, 1988).
The theoretical constructs inherent in the new theoretical perspectives include developmental
contextualism (Lerner, 1998), reciprocal interaction and bidirectionality
(Cairns, 1997), and holistic interactionism (Magnusson, 1999). We refer to these concepts
collectively as within a model of dynamic integration. This concept is evoked to replace
the concept of interaction, which connotes a specific statistical approach.
Contextualism
The interest in the influence of contexts (as conceptualized in peer, family, and neighborhood)—
developmental contextualism (Lerner, 1998)—parallels life span developmental
theory. The life span perspective consists of a composition of ideas about the
nature of human development from birth to death. It is concerned with the embeddedness
of evolution and ontogeny, of consistency and change, of human plasticity, and of
the role that developing persons play in their own development (Lerner, 1987). Thus, a
life span perspective played a formative role in the genesis of contextualism, a concept
that integrates biological and psychological levels with the contextual levels of analysis.
Reciprocal Interaction and Bidirectionality
The systems, or configural and bidirectional, perspective views processes from different
levels as having equal potencies in development (Cairns, 1997; Lerner, 1998; Magnusson,
1999; Susman, 1997, 1998). The biological changes that transpire both influence
and reciprocally are influenced by psychological, behavioral, and social influences.
Plasticity
Plasticity is inherent to the concept of dynamic integration, as plasticity evolves from
the notion that the potential for change exists in the multiple levels of organization that
characterize the developing human (Lerner, 1998). Developmental plasticity at puberty
has constraints imposed from both endogenous (e.g., genetic) and exogenous (e.g., nutrition)
sources. The degree of plasticity in pubertal processes is influenced by genes,
Puberty: An Integrated Biosocial Perspective 17
neuroendocrine systems, experiential history, and the multiple contexts of development.
However, plasticity is relative because all developmental modifications are neither desirable
nor possible and the normative age of onset of puberty is narrow.
Interactionism
Magnusson (1999) brought together the concepts of contextualism, reciprocal interaction,
and bidirectionality in his metamodel of holistic interactionism. A basic proposition
of an interactionism framework is that the individual is an active, intentional
part of an integrated, complex, continuous, dynamic, reciprocal, and adaptive personenvironment
system from the fetal period until death (Magnusson, 1999; Magnusson &
Cairns, 1996). Novel patterns of functioning arise during ontogeny, and differences in
the rates of development, like differences in timing of puberty, may produce unique organization
and configuration of psychological functions that are extremely sensitive to
the environmental circumstances in which they are formed (Magnusson & Cairns,
1996). Until the last few decades the role of the environment on modulating pubertyrelated
neuroendocrine processes at puberty was rarely considered.
Dynamic Integration
Dynamic integration embodies the notion that biological processes depend on and simultaneously
are dependent on the psychological and social contextual levels of functioning.
Consistent with the holistic interactionism perspective, the developmental integration
model views development at puberty as the merging of levels of functioning.
A fundamental premise is that development proceeds through integration rather than
compartmentalization of psychological, biological, and contextual processes. For instance,
genes no longer are considered deterministic influences on development. Rather,
genes are viewed as requiring a specific environment in which to be expressed. Furthermore,
genetic influences are not static but change expression across development.
Genes responsible for pubertal development, such as gonadotropin releasing hormone
(GnRH) genes, begin to stimulate mRNA in late childhood, leading to a cascade of hormonal
and physical growth changes. Thus, the physical and hormonal manifestations
of puberty are a product of a species genotype. Nonetheless, genetic expression is proposed
to be integrated with the experiential history of adolescents and the contexts for
social interactions to change behavior at puberty. The physical changes are integrated
with the adolescent’s psychological attributes, experiences, the timing of the change relative
to peers, and the social context in which puberty occurs, which give meaning to
puberty. Thus, a dynamic integration perspective focuses on the simultaneous integration
among these levels of analysis, such as the integration of hypothalamic, pituitary,
and gonadal hormones to bring about physical change, as well as the integration of psychological
processes and social contexts to produce psychological development.
An integrated model does not imply that all aspects of puberty are considered simultaneously.
Rather, the developmental integration model, as is the case for the developmental
contextual and holistic interaction models, acts as a guide for selecting
constructs and measures. Within this perspective, developmental processes are accessible
to systematic scientific inquiry because they occur in a specific way within organ-
18 Puberty and Psychological Development
ized structures and are guided by specific principles. Critical to integration models is
the interpretation of findings at one level of functioning in relation to levels above and
below the level of empirical verification.
BIOLOGY OF PUBERTY
Puberty (Latin, pubertas, from pubes, puber, of ripe age, adult) can be defined as “the
state of physical development at which persons are first capable of begetting or bearing
children” (Webster’s New Universal Unabridged Dictionary, 1979). This strictly eventdriven
definition is clearly the culmination of a process that began much earlier and encompasses
many parallel processes (as discussed later). Puberty in the human is a unique
and integrated transition from childhood to young adulthood that culminates in the attainment
of fertility. It marks the time of greatest growth and sexual development since
the fetal stages, and it is marked by development of the secondary sexual characteristics
for each gender as well as major alterations in linear growth, body composition,
and the regional distribution of body fat. All are subserved by qualitative and quantitative
alterations in multiple hypothalamic-pituitary end organ axes, especially those
for the gonad and the growth hormone (GH)/insulin-like growth factors-1 (IGF-I) axis.
Puberty is the process of physical maturation manifested by an impressive acceleration
of linear growth in middle to late childhood and the appearance of secondary sexual
characteristics. The secondary sexual characteristics are a result of androgen production
from the adrenals in both sexes (adrenarche or pubarche), testosterone (T)
from the testes in the male, and estrogens from the ovaries in females (gonadarche).
These processes are separate and distinct in origin and timing. Although the rapid
growth spurt had previously been attributed to the rising concentrations of gonadal
steroid hormones, it is an indirect effect that is mediated through altered growth hormone
release and in which insulin-like growth factor I (IGF-I) predominates (Veldhuis,
Roemmich, & Rogol, 2000).
The traditional ages of the beginning of normal pubertal development have been 8
years for girls and 9 years for boys. The external manifestations of this onset have been
considered the development of breast tissue in the girls and testicular enlargement in
boys. The processes leading to these physical signs begin several years earlier, and recent
advances in the ability to measure gonadal and adrenal steroid hormones show
that several years before the physical signs there is evidence for the reawakening of the
hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-adrenal (HPA)
axes. More recent data in girls suggest that breast development (thelarche) and pubic hair
development (adrenarche) are being noted even earlier, and thus the definition of precocious
development likely should be considered a year or more earlier (Herman-Giddens
et al., 1997; Kaplowitz, Oberfield, et al., 1999). The more recent data for boys has not
shown any trend toward earlier maturation (Biro, Lucky, Huster, & Morrison, 1995).
Secondary Sexual Characteristics
The method of Tanner (stages 1–5) is the most commonly used throughout the world to
assess sexual maturation (Tanner, 1962). A similar rating scale is utilized for pubic hair.
Biology of Puberty 19
Although pubic hair may be the first external sign of puberty in some boys, reddening
and thinning of the scrotum and increased testicular size are the first physical findings
of gonadarche (puberty). During puberty in the male the larynx, cricothyroid cartilage,
and laryngeal muscles enlarge; the voice breaks at approximately 13.9 years, and the
adult voice is attained by approximately 15 years (Karlberg & Taranger, 1976), a welcome
relief for boys.
The appearance of breast buds is normally the first external sign of pubertal development
(gonadarche) in girls. The growth spurt (discussed later) occurs earlier in the
sequence of puberty in girls than in boys and often occurs with minimal breast development.
The pace of pubertal development correlates with the levels of sex steroid hormones
during early puberty (DeRidder et al., 1992). In girls the duration of puberty is
usually 3 to 3.5 years, but puberty may be completed within 2 years or take up to 5 to 6
years to complete (Zacharias, Wurtman, & Shatzoff, 1970). Menarche is a late sign of
pubertal development and occurs approximately 2.5 years after thelarche.
Growth
One of the hallmarks of pubertal development is an acceleration in linear growth velocity,
or the adolescent growth spurt. As puberty approaches, the growth velocity reaches
a minimum (the preadolescent dip) before it accelerates during midpuberty. The timing
of the pubertal growth spurt occurs earlier in girls (typically at Tanner breast stage 3)
and does not reach the magnitude that it does in boys. Girls average a peak height velocity
of 9 cm/yr at age 12 and a total gain in height of 25 cm during pubertal growth
(Marshall & Tanner, 1969). Boys attain a mean peak height velocity of 10.3 cm/yr, on
average 2 years later than the girls, during Tanner genital stage 4, and gain 28 cm in
height (Marshall & Tanner, 1970). The longer duration of pubertal growth in combination
with a greater peak height velocity results in the average adult height difference
of 13 cm between men and women (Tanner, 1989). Following a period of decelerating
height velocity, growth virtually ceases due to epiphyseal fusion, typically at a skeletal
age of 15 years in girls and 17 years in boys.
Puberty is also a time of significant weight gain: 50% of adult body weight is gained
during adolescence. In boys, peak weight velocity occurs at about the same time or
slightly later than peak height velocity (age 14 years) and averages 9 kg/year. In girls,
the peak weight velocity lags behind the peak height velocity by approximately 6
months and reaches 8.3 kg/yr at about age 12.5 years (Barnes, 1975; Tanner, 1965). The
rate of weight gain decelerates in a fashion similar to height velocity during the latter
stages of pubertal development.
Marked changes in body composition, including changes in the relative proportions
of water, muscle, fat, and bone, occur during pubertal development and result in the
typical male-female physiques. Under the influence of the gonadal steroid hormones
and the hormones of the growth hormone IGF-I axis, increases in bone mineral content
and muscle mass occur, and the deposition of fat is maximally sexually dimorphic.
The changes in the distribution of body fat (central vs. peripheral, subcutaneous vs. visceral,
and upper vs. lower body) result in the typical android and gynecoid patterns of
the older adolescent and adult (van Lenthe, van Mechelen, Kemper, & Twisk, 1998).
20 Puberty and Psychological Development
Differential growth of the shoulders and the pelvis and differences in lean tissue accrual
between males and females are also prominent.
Under the influence of T, boys have a significant increase in bone and muscle growth
with a simultaneous loss of fat in the limbs (Malina & Bouchard, 1991). The maximal
loss of fat and increase in muscle mass in the upper arms correspond to the time of peak
height velocity. The significant increase in lean body tissue exceeds the total weight gain
due to the simultaneous loss of body fat. As height velocity slows, fat accumulation resumes
in both genders but is twice as rapid in girls than in boys (Malina & Bouchard,
1991). Adult men have 1.5 times the lean body mass as the average female and twice the
number of muscle cells. The increases in the skeleton and in muscle mass underlie the
increased strength of the male. Both androgens and estrogens promote deposition of
bone mineral, and more than 90% of the peak skeletal mass is present by age 18 years
in adolescents who have progressed through pubertal development at the usual ages. In
girls, nearly one third of the total skeletal mineral is deposited in bone during the 3- to
4-year period immediately after the onset of pubertal development (Bonjour, Theintz,
Buchs, Slosman, & Rizzoli, 1991; Slemenda et al., 1994). Adolescents with delayed puberty
or secondary amenorrhea may fail to accrue bone mineral density normally and
take a reduced peak bone mineral content into the rest of their life span, with obvious
implications for osteoporosis and bony fractures later in development.