Adolescent Development week 2

2.1 | Overview of Puberty

What is Puberty?

Puberty is a biological transition that marks the beginning of adolescence and initiates the body’s progression toward sexual and reproductive maturity. This process is regulated by the endocrine system, particularly the hypothalamic–pituitary–gonadal (HPG) axis. It begins when the hypothalamus increases its production of gonadotropin-releasing hormone (GnRH), which prompts the pituitary gland to release:

• Luteinising hormone (LH)

• Follicle-stimulating hormone (FSH)

These hormones travel to the gonads (testes in boys, ovaries in girls), where they stimulate the production of sex hormones—primarily oestrogens and androgens. These hormonal changes lead to a range of physical, cognitive, and emotional changes that unfold over several years.

A hallmark of puberty is the development of primary and secondary sex characteristics:

• Primary sex characteristics: Changes directly related to reproductive function (e.g., spermatogenesis in boys, menarche in girls)

• Secondary sex characteristics: Observable physical traits (e.g., breast development, deepening of the voice, growth of pubic/underarm hair, body composition changes)

Another defining feature is the growth spurt, a rapid increase in height and weight triggered by growth hormone and sex steroids. Girls typically begin this phase earlier than boys. Other changes include:

• Increased bone density, organ size, and body proportions

• Skin changes (e.g., oil production, acne)

• Sleep shifts, influenced by melatonin changes

• Altered metabolism, affecting energy and appetite

Although puberty follows a predictable biological sequence, there is considerable variation in onset, duration, and pace. For most individuals, it begins:

• Between ages 8–13 in girls

• Between ages 9–14 in boys

Two key phases include:

• Adrenarche: Early increase in adrenal androgens before visible signs of puberty

• Gonadarche: Full activation of the HPG axis, initiating sexual maturation

Puberty is not only physical—it significantly impacts psychological development, self-concept, and social relationships, laying the foundation for adult identity and long-term health outcomes.

Trends in Pubertal Onset

Over the past 150 years, there has been a secular trend toward earlier pubertal onset, particularly in industrialised countries. For example:

• In Europe, the average age of menarche dropped from 16–17 years in the 19th century to 12–13 years today

• Improvements in nutrition, healthcare, and living conditions largely explain this shift

• This trend appears to be plateauing in some high-income countries

In Australia, the average age of menarche is now approximately 12.9 years. Data from longitudinal studies like the Raine Study confirm this secular decline (Huynh et al., 2022). However, differences exist between population subgroups:

• Evidence suggests Aboriginal and Torres Strait Islander girls may experience slightly earlier menarche than non-Indigenous peers, although research is limited (Bird et al., 2022)

• Cross-cultural comparisons show earlier puberty in:

  • High socioeconomic status groups

  • Populations with Westernised diets and urban lifestyles

  • Later onset in rural/high-altitude communities or under-resourced areas

Factors impacting onset

1. Genetics

Genetic factors are central in determining the timing of puberty. Studies show:

• Heritability estimates of pubertal timing range from 50–80%

• Monozygotic twins typically enter puberty at similar ages

• Strong correlations exist between mothers' and daughters' age at menarche

Genome-wide association studies (GWAS) have identified specific genes (e.g., LIN28B, KISS1) that regulate the HPG axis and influence pubertal timing (Perry et al., 2014; Elks et al., 2010). However, environmental and psychosocial factors can moderate genetic effects.

2. Diet, Nutrition, and Body Fat

Nutritional status strongly influences puberty, especially in girls:

• A body fat percentage of ~17% is typically required for menarche to occur

• Leptin, a hormone produced by fat cells, signals energy sufficiency to the hypothalamus and initiates GnRH secretion

• Undernutrition or extremely low body fat (e.g., in eating disorders or athletes) can delay puberty by suppressing the HPG axis

Conversely:

• Diets high in energy-dense, processed foods are associated with earlier onset

• Both quantity and quality of caloric intake matter (Kaplowitz, 2008; Soliman et al., 2014)

3. Psychosocial Stress

Early-life stress has a complex impact on puberty:

• Moderate psychosocial stress (e.g., family conflict, father absence) is associated with earlier puberty, especially in girls

• This aligns with life history theory, which posits that stress signals environmental unpredictability and accelerates reproductive maturation (Belsky et al., 2007)

• Cortisol, the stress hormone, can influence the HPG axis and stimulate earlier GnRH activation

However, severe or chronic trauma may delay puberty in some cases, depending on individual resilience and contextual support (Mendle et al., 2007; Graber et al., 1995)

4. Sleep

Sleep is emerging as a key factor in pubertal timing due to its effect on neuroendocrine function:

• Short sleep duration is associated with earlier pubertal onset, possibly via:

  • Disrupted melatonin secretion

  • Changes in leptin and insulin resistance

• Poor sleep quality is linked to earlier secondary sex characteristic development in girls

By contrast, longer and more regular sleep patterns have been associated with delayed puberty in some populations (Wu et al., 2023; Crowley et al., 2007). Given rising rates of adolescent sleep deprivation, sleep may be a modifiable protective factor for healthy development.

5. Physical Activity

The level of physical activity also influences pubertal timing:

• High-intensity training (especially among elite athletes) can delay puberty by:

  • Reducing body fat

  • Suppressing reproductive hormones (Rogol et al., 2000)

• Sedentary lifestyles and low physical activity are linked to:

  • Higher BMI

  • Earlier menarche (Tong et al., 2020)

Moderate, regular exercise is associated with more typical pubertal trajectories, helping maintain metabolic balance and healthy body composition.

Key Concepts/Definitions

• Puberty: A biological transition marking the start of adolescence, driven by hormonal changes through activation of the hypothalamic–pituitary–gonadal (HPG) axis, leading to sexual and reproductive maturity.

• Primary and secondary sex characteristics: Primary characteristics involve reproductive organs and functions (e.g., spermatogenesis, menarche), while secondary characteristics include visible physical changes like breast development and voice deepening.

• Growth spurt: A rapid increase in height and weight during puberty, influenced by growth hormone and sex steroids, typically occurring earlier in girls than boys.

• Phases of puberty: Puberty occurs in stages, including adrenarche (increase in adrenal androgens) and gonadarche (activation of the HPG axis and sexual maturation).

• Secular trend in pubertal timing: A historical decline in the average age of pubertal onset, especially menarche, due to improved nutrition and health, most evident in industrialised countries.

• Genetics: Genetic factors strongly influence the timing of puberty, with specific genes (e.g., LIN28B, KISS1) regulating HPG axis activity and contributing to individual variation.

• Diet and body fat: Nutritional status and fat composition affect pubertal onset; higher body fat and energy-dense diets are linked to earlier puberty, while undernutrition can delay development.

• Psychosocial stress: Early-life stressors such as conflict or father absence may accelerate puberty in girls through hormonal pathways, though extreme trauma can sometimes delay development.

• Sleep: Sleep quantity and quality influence pubertal timing; insufficient or irregular sleep may contribute to earlier onset, possibly via hormonal disruptions.

• Physical activity: High levels of intense activity can delay puberty due to reduced fat stores, while low activity and sedentary behaviour are associated with earlier onset through increased body fat.

2.2 | Puberty in Females

Initiation of Puberty in Females

Puberty in females begins with the activation of the hypothalamic–pituitary–gonadal (HPG) axis, a neuroendocrine feedback loop responsible for regulating sexual maturation. This process generally starts between 8 and 13 years of age, when:

• The hypothalamus releases gonadotropin-releasing hormone (GnRH) in a pulsatile manner

• GnRH stimulates the pituitary gland to release:

  • Luteinising hormone (LH)

  • Follicle-stimulating hormone (FSH)

• LH and FSH stimulate the ovaries, initiating oestrogen production

Although genetically programmed, the timing of puberty can be influenced by environmental factors such as nutrition, body composition, and overall health.

The ovaries produce oestrogens (primarily oestradiol), which drive key changes:

• Maturation of reproductive organs (uterus, vagina)

• Breast development

• Regulation of the menstrual cycle 

• Changes in:

  • Skeletal growth

  • Fat distribution

  • Secondary sex characteristics

PHYSICAL CHANGES

The first visible sign of female puberty is usually thelarche (breast development), followed by pubarche (growth of pubic and underarm hair). These are considered secondary sex characteristics and are influenced by rising levels of oestrogens and adrenal androgens.

Physical development typically follows the Tanner stages:

• Occurs over several years

• Used to track and assess sexual maturation

TANNER STAGES

Stage 1 (Prepubertal)

• No breast development (flat chest with raised nipple only)

• No pubic hair

Stage 2

• Small breast buds form

• Areola begins to enlarge

• Sparse, lightly pigmented pubic hair appears along the labia

Stage 3

• Continued enlargement of breast and areola

• Still a single breast mound

• Pubic hair becomes darker, coarser, starts to spread over pubic bone

Stage 4

• Areola and nipple form a secondary mound above the breast contour

• Pubic hair is fuller but does not yet spread to the thighs

Stage 5 (Mature Stage)

• Breasts reach full adult size and shape

• Areola recedes to the general contour of the breast

• Adult-type pubic hair extends to the inner thighs

Other physical changes include:

• Internal growth of the uterus, vagina, and fallopian tubes

• Increase in body fat, especially around the hips and thighs

• Changes in skin texture and oil production, which may lead to acne

• A growth spurt, with peak height velocity typically occurring before menarche

• Physical changes contribute to readiness for reproduction and may affect body image

Key Concepts/Definitions

• Initiation of puberty in females: Begins with activation of the hypothalamic–pituitary–gonadal (HPG) axis, which regulates hormonal signals leading to sexual maturation.

• Gonadotropin-releasing hormone (GnRH): A hormone released by the hypothalamus that stimulates the pituitary gland to secrete luteinising hormone (LH) and follicle-stimulating hormone (FSH).

• Oestrogen: The primary female sex hormone produced by the ovaries, responsible for the development of reproductive organs, breast growth, and menstrual cycle regulation.

• Primary sex characteristics: Changes directly related to reproductive function, such as the maturation of the uterus, ovaries, and onset of menarche.

• Secondary sex characteristics: Observable physical changes not directly involved in reproduction, including breast development, pubic hair growth, and changes in body fat distribution.

• Thelarche and pubarche: Thelarche refers to breast development, and pubarche refers to the appearance of pubic and underarm hair—both are early signs of female puberty.

• Tanner stages: A five-stage scale used to track the progression of physical sexual development in girls, based on breast and pubic hair growth.

• Growth spurt: A rapid increase in height and weight during puberty, typically occurring earlier in girls and often peaking before menarche.

• Menarche: The first menstrual period, usually occurring around ages 12–13, marking potential reproductive capability but not full reproductive maturity.

• Anovulatory cycles: Menstrual cycles that occur without ovulation, which are common in the early years after menarche as hormonal regulation stabilises.

MENARCHE

• Menarche: first menstrual period, typically around ages 12–13

  • Marks fertility potential, though ovulation may be inconsistent at first

  • Regulated by LH, FSH, and ovarian hormones

• Anovulatory cycles (menstrual cycles without ovulation) common in early years

• Hormonal rhythms take years to stabilize

• Reproductive maturity continues to develop through late adolescence and adolescents build psychosocial competence

• Experiences of menstruation shaped by individual, familial, and cultural factors influencing how it is perceived and managed.

Key Concepts/Definitions

• Initiation of puberty in females: Begins with activation of the hypothalamic–pituitary–gonadal (HPG) axis, which regulates hormonal signals leading to sexual maturation.

• Gonadotropin-releasing hormone (GnRH): A hormone released by the hypothalamus that stimulates the pituitary gland to secrete luteinising hormone (LH) and follicle-stimulating hormone (FSH).

• Oestrogen: The primary female sex hormone produced by the ovaries, responsible for the development of reproductive organs, breast growth, and menstrual cycle regulation.

• Primary sex characteristics: Changes directly related to reproductive function, such as the maturation of the uterus, ovaries, and onset of menarche.

• Secondary sex characteristics: Observable physical changes not directly involved in reproduction, including breast development, pubic hair growth, and changes in body fat distribution.

• Thelarche and pubarche: Thelarche refers to breast development, and pubarche refers to the appearance of pubic and underarm hair—both are early signs of female puberty.

• Tanner stages: A five-stage scale used to track the progression of physical sexual development in girls, based on breast and pubic hair growth.

• Growth spurt: A rapid increase in height and weight during puberty, typically occurring earlier in girls and often peaking before menarche.

• Menarche: The first menstrual period, usually occurring around ages 12–13, marking potential reproductive capability but not full reproductive maturity.

• Anovulatory cycles: Menstrual cycles that occur without ovulation, which are common in the early years after menarche as hormonal regulation stabilises.

2.3 | Puberty in Males

Puberty in males typically begins between the ages of 9 and 14, although the timing can vary. As in females, the process is triggered by the activation of the hypothalamic–pituitary–gonadal (HPG) axis:

• The hypothalamus releases gonadotropin-releasing hormone (GnRH)

• GnRH stimulates the pituitary gland to secrete:

  • Luteinising hormone (LH)

  • Follicle-stimulating hormone (FSH)

• These hormones act on the testes, increasing the production of testosterone, the primary male sex hormone (Steinberg et al., 2023; Santrock, 2019)

Testosterone is responsible for the development of both primary sex characteristics (reproductive organs) and secondary sex characteristics. Although initial hormonal changes are internal, the first external sign of male puberty is testicular enlargement, marking the beginning of a complex, multi-year transformation involving growth, muscular development, and voice changes (Parent et al., 2003).

Physical Changes in MALES

The first observable physical change in male puberty is testicular enlargement, followed by:

• Thinning and darkening of the scrotal skin

• Penile growth (first in length, then in girth)

• Development of pubic, underarm, and facial hair due to adrenal and testicular androgens (Marshall & Tanner, 1970; Rogol et al., 2000)

Additional secondary physical changes include:

• A growth spurt, usually peaking around ages 13.5 to 14.5 (later than in females)

• Increased muscle mass and shoulder broadening

• Deepening of the voice due to changes in the larynx and vocal cords

• Increased sebaceous gland activity (acne) and noticeable sweating

These changes generally follow a predictable sequence, tracked using the Tanner stages.

TANNER STAGES

Stage 1 (Prepubertal)

• Genitalia are small and consistent with prepubertal anatomy

• Scrotal skin is smooth and lacks darkening or textural change

• No pubic hair present

Stage 2

• Testes begin to enlarge

• Scrotal skin thins, reddens, and begins to change in texture

• Sparse, lightly pigmented pubic hair appears at the base of the penis

Stage 3

• Continued testicular growth

• Penis begins to lengthen, but girth remains mostly unchanged

• Pubic hair becomes darker, coarser, and starts to spread

Stage 4

• Penis continues to grow in length and now increases in girth

• Scrotum darkens and further develops

• Pubic hair is fuller but does not yet extend to the thighs

Stage 5 (Mature Stage)

• Genitalia reach adult size and shape

• Pubic hair is adult in quantity and distribution

• Hair may spread to the inner thighs and lower abdomen

SPERMENARCHE

A key milestone in male puberty is spermarche, the first ejaculation containing viable sperm. It usually occurs between ages 12 and 14 and may happen during a nocturnal emission (a "wet dream"). Spermarche signals the onset of biological fertility and follows:

• Maturation of testicular tissue

• Increased FSH and LH, which stimulate sperm production in the seminiferous tubules (Steinberg et al., 2023; Santrock, 2019)

However, reproductive maturity develops gradually. In early adolescence:

• Sperm counts may be low and inconsistent

• Full reproductive function takes time to stabilise

Hormonal rhythms and physical development continue to progress into the late teen years, culminating in:

• A fully mature reproductive system

• Adult-level secondary sex characteristics

• Foundations for sexual functioning and long-term reproductive health

Key Concepts/Definitions

• Initiation of puberty in males: Begins between ages 9 and 14 and is triggered by activation of the hypothalamic–pituitary–gonadal (HPG) axis, leading to hormonal changes.

• Testosterone: The primary male sex hormone produced by the testes, responsible for the development of reproductive organs and secondary sex characteristics.

• Primary sex characteristics: Physical changes directly related to reproduction, including testicular enlargement, scrotal changes, and penile growth.

• Secondary sex characteristics: Bodily changes not directly tied to reproduction, such as facial hair growth, deepening of the voice, acne, and increased muscle mass.

• Growth spurt: A rapid increase in height and bone growth during puberty, typically occurring later in boys than in girls, around ages 13.5 to 14.5.

• Tanner stages: A five-stage scale used to track male physical development, including changes in genital size, scrotal skin, and pubic hair distribution.

• Spermarche: The first ejaculation containing viable sperm, usually occurring between ages 12 and 14, marking the onset of biological fertility.

• Reproductive maturity: Develops gradually after spermarche, with sperm production becoming more consistent over time and full function reached in the late teens.

• Androgens: Hormones including testosterone and adrenal androgens that drive the development of male secondary sex characteristics.

• Physical changes: Include voice deepening due to larynx growth, increased sweating, acne from sebaceous gland activity, and broadening of the shoulders.

2.4 | Cultural, Social, and Psychological Responses to Puberty

CULTURAL RESPONSES TO PUBERTY

Across cultures, puberty is not only a biological event but also a social and spiritual milestone. In many traditional societies, it marks the transition from childhood to adulthood and is celebrated through initiation rites or coming-of-age ceremonies. These rites serve several functions:

• Help adolescents understand their new social roles and responsibilities

• Reinforce cultural identity, values, and belonging

• Involve guidance or instruction from elders

For example, in some cultures, menarche is celebrated as a girl’s entry into womanhood, while boys may undergo symbolic or physical trials to mark manhood. These events signal readiness for adult responsibilities and community participation.

Rituals around puberty vary globally, reflecting cultural values about gender, adulthood, and social roles:

• In sub-Saharan Africa, puberty ceremonies may involve extended seclusion and instruction about marriage, sexuality, and community expectations

• In Japan, the Seijin Shiki (Coming of Age Day) celebrates 20-year-olds, though earlier physical maturation may also receive recognition

• In Latin America, the quinceañera marks a girl’s 15th birthday, often following menarche, as a transition into womanhood

• In conservative or patriarchal cultures, puberty—especially for girls—may lead to increased restrictions, surveillance, or even early marriage

These practices shape how adolescents interpret and adapt to their changing bodies. Whether celebratory or restrictive, they influence the meaning of puberty within each cultural context.

Aboriginal and Torres Strait Islander Contexts

Among Aboriginal and Torres Strait Islander peoples, puberty has traditionally been a time for:

• Spiritual growth

• Connection to kin and Country

• Preparation for adulthood

Practices vary across communities, but often include ceremony, storytelling, seclusion, and the transmission of gender-specific cultural knowledge. For example:

• Boys may participate in initiation rites such as circumcision and receive teachings from male Elders about Lore, hunting, and responsibility

• Girls, upon menarche, may experience seclusion and be cared for by female relatives while learning about their roles as caregivers, cultural custodians, and knowledge holders (Lowitja Institute, 2018; Queensland Government, 2023)

Although colonisation and historical trauma disrupted many of these traditions, efforts are underway to revive or adapt puberty rites within culturally safe, contemporary frameworks. Community programs now often blend traditional teachings with modern health education, supporting:

• Identity development

• Resilience and emotional well-being

• Cultural connection and belonging

These culturally grounded approaches serve as protective factors that affirm self-worth and promote holistic development.

SOCIAL PERCEPTIONS OF EARLY MATURATION

• Physical maturity may lead to being treated as older or more responsible

• Mismatch between appearance and emotional readiness can create tension

• Early-maturing girls may attract unwanted attention from older peers/adults which can be distressing if not met with appropriate guidance.

• Early-maturing boys may gain peer approval, but also face pressure to perform or act tough

• Can lead to confusion, stress, emotional suppression or risk-taking behaviour if unsupported

Peer Relationships

Peer dynamics are deeply affected by pubertal timing. Physical changes can influence social status, particularly in settings where appearance is highly valued. Adolescents who mature earlier or later than their peers may feel:

• Out of place, increasing risk of exclusion or bullying

• Self-conscious or anxious, especially if they stand out physically

For example:

• Late-maturing boys may be teased and experience lower social confidence

• Early-maturing boys may enjoy short-term social advantages

• Early-maturing girls may face relational aggression or unwanted sexualised attention

Peer influence becomes more powerful during this period, shaping how adolescents behave and how they emotionally respond to their changing bodies.

Family Relationships

Within the family, puberty often brings shifts in dynamics and expectations. Adolescents typically seek greater autonomy, prompting adjustments in:

• Household roles

• Privacy boundaries

• Rules around modesty and social activities

Some families, especially within cultures that closely link female maturity with sexuality or honour, may become more protective of daughters during puberty. How families respond—whether with openness, embarrassment, or strict control—influences adolescents’ self-image and comfort in discussing bodily changes. Supportive, communicative families can buffer the stress of puberty and help young people adjust more positively.

SELF PERCEPTIONS AND PACE OF DEVELOPMENT

Puberty also brings major psychological changes, shaped by hormonal shifts, social experiences, and self-perception. Adolescents become increasingly aware of their physical development and may feel:

• Self-conscious or uncertain

• Distressed by early or late maturation relative to peers

This is especially true for early-maturing girls, who are at increased risk for:

• Anxiety and depression

• Body dissatisfaction, particularly in social contexts that sexualise female bodies

Late-maturing boys may experience lowered self-esteem and challenges related to social comparison.

EMOTIONAL VOLATILITY AND VULNERABILITY

Hormonal changes can heighten emotional reactivity, leading to:

• Mood swings

• Greater stress sensitivity

• Amplified responses to feedback and social cues

These shifts are normal, but may become problematic in unsupportive environments or when adolescents lack coping skills. The combined influence of hormonal surges and brain changes in emotion regulation makes early adolescence especially vulnerable to internalising problems.

IDENTITY EXPLORATION AND RESILIENCE

Yet puberty also fosters psychological growth. As adolescents become more physically mature, they begin to engage with:

• Identity development

• Future planning

• Abstract thinking about self and others

Physical changes may trigger body awareness, exploration of gender identity, sexuality, and evolving social roles. For some, puberty represents an empowering step toward autonomy and adult identity.

How adolescents experience and emotionally process puberty depends on multiple factors:

• Biological timing

• Family communication

• Peer support

• Cultural messages

• Personal resilience

These factors shape whether puberty is experienced as confusing, stressful, affirming, or empowering.

Key Concepts/Definitions

• Cultural responses to puberty: Puberty is often marked by rituals or ceremonies that symbolise the transition to adulthood, reinforcing cultural identity and social roles through practices such as instruction, seclusion, or symbolic trials.

• Initiation rites: Traditional practices in many cultures that mark puberty, such as circumcision for boys or menarche ceremonies for girls, often include teachings from Elders and gender-specific knowledge transmission.

• Cultural variation in puberty rituals: Practices differ globally—ranging from the quinceañera in Latin America to Seijin Shiki in Japan—and reflect local beliefs about gender, adulthood, and social responsibility.

• Aboriginal and Torres Strait Islander puberty practices: Puberty is a time for spiritual growth, kinship teachings, and connection to Country, with gender-specific ceremonies that promote identity and cultural continuity.

• Revitalisation of traditional practices: Some Indigenous communities are reclaiming or adapting puberty rites through culturally safe programs that integrate traditional knowledge with modern health education.

• Social responses to puberty: Physical changes can lead to altered expectations from parents and peers, often resulting in mismatches between appearance and emotional readiness, and influencing autonomy and peer dynamics.

• Psychological responses to puberty: Hormonal and bodily changes can affect mood, self-image, and mental health, especially for early or late maturers; interpretation of these changes is shaped by support systems and cultural context.

2.5 | Evolution, Heredity, & the Environment

Evolution and Behaviour

Evolutionary theory helps explain adolescent development by proposing that certain traits were shaped by natural selection because they once offered survival or reproductive advantages.

• Traits such as risk-taking, sensation-seeking, and sexual motivation may have helped early humans leave home, find mates, and adapt to new environments.

• These behaviours, though sometimes seen as problematic today, may reflect evolutionary adaptations.

Even adolescent brain development can be viewed through this lens:

• The limbic system (emotion/reward) matures earlier than the prefrontal cortex (regulation/decision-making), which may have promoted adaptive learning through trial and error.

• In modern society, however, these patterns can increase vulnerability to risky behaviours if not balanced by supportive environments.

EPIGENETICS AND ENVIRONMENTAL INFLUENCE

• Gene expression can change without altering the DNA sequence

• Epigenetics = study of how environment influences gene activity

• Stress, trauma, nutrition can activate or silence genes

• Examples: chronic stress may alter genes involved in emotional regulation

• Gene expression is especially sensitive during adolescence

• Heredity = blueprint, but expression depends on environment

ENVIRONMENT SHAPES GENETIC POTENTIAL

• Environment influences how genes are expressed

• Begins in prenatal period (e.g., maternal health, substance exposure)

• In adolescence, key postnatal factors include:

  • Nutrition

  • Education

  • Peer relationships

  • Culture

  • Socioeconomic status

• Twin studies show that identical genes can lead to different outcomes in different environments

  • For example: Two adolescents with similar academic potential may differ significantly in achievement based on access to educational resources or supportive home environments.

TIMING, PLASTICITY AND VULNERABILITY

Adolescents are especially sensitive to environmental inputs due to:

• Ongoing neural plasticity

• Heightened emotional reactivity

• Increased independence

This creates both opportunities for growth and vulnerabilities, depending on the quality and consistency of their surroundings.

Genotype → Environment Effects

Sandra Scarr’s genotype → environment theory describes how genetics and environment interact in three key ways:

1. Passive gene–environment correlation

   • Parents pass on genes and shape environments.

   • E.g., A verbally skilled parent provides books and the genes for verbal ability.

2. Evocative gene–environment correlation

   • A child’s traits elicit reactions from others.

   • E.g., A cheerful child receives more positive attention.

3. Active gene–environment correlation (niche-picking)

   • Individuals choose environments that match their genetic tendencies.

   • E.g., A musically talented teen may join a band or enrol in music electives.

During adolescence:

• Active effects become more prominent as independence increases.

• Example: An extroverted adolescent may seek out social clubs or leadership roles, further reinforcing extroverted behaviours.

Key Concepts/Definitions

• Evolutionary theory: Explains adolescent traits like risk-taking and social exploration as adaptations that were once advantageous for survival and reproduction.

• Heredity: The transmission of genetic traits from parents to offspring via DNA, influencing characteristics such as temperament, intelligence, and mental health.

• Polygenic traits: Traits influenced by multiple genes, rather than a single gene, common in areas like personality and cognitive ability.

• Epigenetics: The study of how environmental factors can regulate gene expression without altering DNA, showing how experiences like stress can affect development.

• Environmental influences: Factors such as family, education, nutrition, and culture that shape how genetic potentials are expressed during adolescence.

• Genotype → environment effects: A theory describing how genes influence the environments individuals experience through passive, evocative, and active correlations.

• Niche-picking: A form of active gene–environment correlation where adolescents seek out environments that align with their genetic traits.

• Biopsychosocial approach: A holistic perspective recognising that adolescent development results from interactions between biological, psychological, and social factors.