Stages of Adolescence: Everything you need to know

Growing up is something all of the living must experience. Transitioning from childhood to adolescence and then into adulthood does not have to be a stage filled with existential crises and awkward introductions. Whether parenting an adolescent or transitioning into adolescence yourself, half of the battle is knowing what to expect during the stages of adolescence: how adolescence affects the brain, the physical changes of puberty, social development, and cognitive function.

Stages of Adolescence
The need for sleep increases in adolescence.

Stages of Adolescence: What is Adolescence?

Occurring in all cultures and historical periods, adolescence is the stage in life between childhood and adulthood marked by the onset of puberty—a set of biological changes to reach sexual maturity. A number of physical and psychological processes are also involved in the transition from childhood to emerging adulthood, as adolescence is the time when young people are preparing to take on adult responsibility.

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The accepted age for adolescence differs. Adolescence typically starts around age 10 or 11 at the beginning of puberty. According to the US National Library of Medicine, adolescence ends at ages 18 or 19 when adult behavior and identity has been accepted. The adolescent age range is divided into three categories known as stages of adolescence.

Stages of Adolescence: Adolescence and the Brain

A variety of brain changes take place throughout adolescence. These physical changes within the brain lend reason for the “angst” teens are infamous for. The generation of brain connections combined with fluctuating hormones and neurotransmitter levels leaves adolescents susceptible to positive and negative environmental influences. Thus, risk-taking behavior, moodiness, and a lack of impulse control around peers are natural while adjusting to their budding identities and revolutionized capacity for thought on their way to adulthood.

Neurons During the Stages of Adolescence

Although the brain is fully grown shortly after birth, it undergoes extensive structural changes in adolescence. Gray matter is one of the two types of central nervous system tissues containing the brain’s neurons—a specialized nerve cell that sends chemical messages to the body through connections called synapses.

Before adolescence, there is an overproduction of neuronal connections. While it seems the development of the brain in adolescence would cause an increase in neurons, the opposite is actually true! The brain’s synapses are later reduced when cognitive abilities peak with synaptic pruning. Studies reveal that the adolescent brain loses 7-10% of gray matter because unnecessary synaptic connections are eliminated. The brain is faster and more efficient with less neuronal connections. Childhood synapses that are not used are discarded, but the connections used frequently are strengthened as the result of synaptic pruning. This process is similar to pruning a bush to prevent weaker branches from interfering with the potential for growth.

Neurotransmitters in the Stages of Adolescence

Neurotransmitters are chemical substances released by neurons (nerve cells) in the brain. Dopamine, serotonin, and melatonin are the three primary neurotransmitters that decrease during adolescence. A decrease in dopamine and serotonin lead to impulsive, moody behavior. The production of melatonin shifts the circadian rhythm and increases the need for sleep, which is why you will find most teens sleep until noon.

Prefrontal Cortex Development in the Stages of Adolescence

The human brain matures from back to front. Located in the frontal lobe, the pre-frontal cortex is last to develop in comparison to other brain areas and is not fully mature until age 25. It is relevant in executive function processes. Often referred to as the brain’s control center, the pre-frontal cortex regulates emotions, controls behavior, and is involved in planning and decision making.

Experts agree that adults do the majority of their thinking using the front portions of their brain, whereas teenagers operate with the back portion. Synaptic pruning has not refined all of the necessary connections for the pre-frontal cortex to function optimally. The outcome is error in decision making during the stages of adolescence.

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Sex Differences in the Stages of Adolescence

There are evident differences between male and female adolescents. During childhood, levels of the primary sex hormones estradiol and testosterone are equal. However, as adolescence begins these hormones levels shift with girls producing eight times more of estradiol and boys double the testosterone. The role of estradiol in females is to aid in the development of secondary sex characteristics, like breast development, and to prepare fertility functions, while testosterone in males is responsible for sexual maturity.

The varying levels of hormones contribute not only to the physical differences in each stage of adolescence, but also to psychological aspects and milestones of adolescence.

Stages of Adolescence: Early Adolescence

Ages 10 to 14 are the years of early adolescence. The most drastic physical changes of puberty occur in this critical stage of human development. The young person is just preparing to adopt a new concept of self, which affects their body, mind, and social interactions.

Physical Characteristics of Early Stages of Adolescence

As previously mentioned, drastic physical changes occur in early adolescence. Puberty is initiated by a rapid growth spurt.  Secondary sex characteristics develop and primary sex characteristics which indicate the capability for sexual reproduction soon follow.

  • Rapid growth spurt: Weight and height increase suddenly.
  • Arms and legs lengthen: Limbs elongate and do not always grow in the same proportion to the body during an adolescent’s rapid growth spurt. Clumsiness is a consequence.  
  • Body hair: Hair forms under the arms and genitals.
  • Increase production of oil: Skin and hair become oily and acne prone.
  • Perspiration: Sweat increases in amounts and acquires a foul smell.  
  • Breast and hip development: Girls become fuller figured with fat accumulating in the breast and hips as the body prepares for reproduction.
  • Adam’s apple: An enlarged larynx causes males to have a larger vocal cord box with deepening voice.
  • Primary sex characteristics: First menstruation for girls, first ejaculation, penile and testicular growth for boys
  • Sexual interest: Adolescents develop an interest in sex.
  • Sleep:More sleep is needed for optimal functioning in early adolescence.

Cognitive Changes of Early Stages of Adolescence

Like the physical transformation, the cognitive changes of early adolescents are radical. Development of the brain leads to the capacity for complex thinking. As described in the theory of cognitive development by psychologist Jean Piaget, children think in concrete operations prior to adolescence. Thinking is still rigid, focused on the present, and they struggle to apply hypothetical reasoning.

However, thinking advances from concrete operations to formal operations in adolescence. Adolescents develop the capacity for abstract thinking. They are able to reason, weigh the pros and cons of situations, and are less egocentric. With the development of formal operations, adolescents can consider multi-viewpoints while forming opinions of their own.

The development of formal operations in early adolescence usually manifests in personal decision making:

  • Home and school decisions: Abstract thinking is reflected in their work at home and at school; adolescents consider hypothetical decisions and the consequences of their actions (i.e. if I do not do this essay assignment, then I will fail, and if I fail, I will____).
  • Forms thoughts and views: Adolescents form their own opinions regarding moral issues, politics, and ethical dilemmas.  
  • Questions authority: With the formation of opinions, early adolescents become aware of the standards of authority figures, society, and peers; they question such authority and how it aligns with their view.
Stages of Adolescence
Stages of Adolescence

Social and Development of Early Stages Adolescence

The whirlwind of changes in early adolescence inevitably impacts social development. Early adolescents struggle with their identity as they start to understand its importance on the path to adulthood. Rather than basing their identities on personal attributes and interests, they hyper-focus on appearance. Adolescents feel awkward over their changing bodies. They have an overwhelming desire to fit in and conform to what is “normal.”

Relationships also evolve in early adolescence. Teens spend less time with family and more with peers who are exceptionally influential in their need to fit into a group. An influx of hormones causes moodiness. The increase in emotionality strains the relationship with their parents. They test the rules in their questioning of authority.

Stages of Adolescence: Middle Adolescence

Middle adolescence ranges from ages 15 to 18. Puberty is no longer foreign. Those in middle adolescence are more comfortable in their bodies and cherish newfound independence. The purpose of middle adolescence is to further develop the processes originating in the previous stage of adolescence.

Physical Characteristics of Middle Stages of Adolescence

Puberty is completed for girls in middle adolescence. By ages 15 and 16, growth slows as weight and height plateau. The average adult height for females is 5’5. Body fat accumulates in the hips, butt, and chest.

Since boys begin puberty later than girls, the rapid growth continues for boys in middle adolescence. They continue to get taller and develop adult body compositions (ratio of fat to lean muscle mass). Boys experience a rapid accumulation of muscle mass and a decrease in fat. Their bodies broaden, legs widen, and shoulders taper at the waist.  

Cognitive Changes of Middle Stages of Adolescence

The cognitive changes of middle adolescence build upon the abstract, complex thinking formed during early adolescence. Older teenagers have added experience with thinking processes. There here-and-now of early adolescence has passed away. Thoughts are more profound and encompass plans for the future.. Middle adolescents tend to seek instant gratification due to emphasis the brain’s reward center.

Examples of cognitive development in middle adolescence are:

  • Goal setting: Middle adolescents have greater competence in goal setting because they think into the future. Stress over school, test scores, and success emerges.
  • Philosophical thinking: Concepts like politics and morals stand out; they form their own ethical codes and wonder about the meaning of life.
  • Role models: Establishing role models helps emulate their “vision” of how they see themselves.
  • Self-involved: While middle adolescents possess the ability to consider others, thinking remains self-involved to an extent; they have high expectations for their wants/desires, yet a low self-concept.

Social and Emotional Development of Middle Stages of Adolescence

Biological changes decelerate, so the emotions of those in middle adolescence are not as erratic and “moody.” Feelings of love and passion surface as middle adolescents explore romantic relationships. They still worry whether their changed bodies are normal and are concerned with sexual attractiveness.

Peer influence escalates. They rely heavily on popularity amongst friends, leaving them prone to potentially risky behaviors (i.e. sexual encounters, drugs, tobacco, etc.). Parental relationships are distant because of the significance of peers.

Stages of Adolescence
Stages of Adolescence

Stages of Adolescence: Late Adolescence and Emerging Adulthood

Late adolescence is termed as emerging adulthood. It comprises adolescents ages 19 to 25. By age standards, late adolescents are considered adults, but development is not entirely finished. This stage of adolescence has five key features: the age of identity exploration, the age of instability, the age of self-focus, the age of feeling in-between, and the age of possibilities.

Physical Changes of Late Stages of Adolescence

Females in late adolescents are fully developed entering emerging adulthood. Contrarily, males are not. Males in late adolescence and emerging adulthood grow in height, weight, muscle mass, and body hair. Primary sex characteristics are already developed. Susceptibility to physical illness is the lowest during late adolescents. It is the peak of physical health.

Cognitive Changes of Late Stages of Adolescence

The main distinction of cognitive changes in late adolescence is that emerging adults have the skill of expressing their thoughts, feelings, and views to others. Thinking now originates from the front of the brain, lending them the ability to delay gratification. Future accomplishment is exceptionally important.

  • Developed reasoning: Late adolescents have better use of complex thinking; they adequately make informed decisions that are less self-centered.
  • Global concepts: Opinions about global concepts like justice, politics, and patriotism are formed.
  • Expressing ideas: They verbalize their opinions to others and hear both sides to a viewpoint.
  • Shifted focus: They question their role in society and how they can contribute (i.e. career, volunteer work).
  • Examination: Emerging adults examine inner experiences and the meaning of the world.

Social and Emotional Development of Late Stages of Adolescence

Emerging adults are emotionally stable in comparison to their early and middle adolescent counterparts. Identity formation and self-concept is improved. Relationships benefit positively. Friends remain a source of support, family ties are appreciated, and romantic relationships are a serious component of emerging adulthood.

Arnett gives five key features of late adolescence that are apparent in social and emotional development.

  • Age of identity exploration: Emerging adults explore their options in love, sexual orientation, work, and making choices to benefit their purpose. Independence allows them to actively try out these options.
  • Age of instability: As they entertain various life choices, there is little stability. An example of instability is moving out of a parent’s house to live in college dorms.   
  • Age of self-focus: The capacity to focus on others definitely exists, but late adolescence is self-focused because emerging adults attempt to hone on their skills for a productive, purposeful life.
  • Age of feeling in-between: The legal adult age and an emerging adult’s responsibilities do not match. They are in limbo with partial adult responsibility while adjusting to establishing their identities.
  • Age of possibilities:Possibilities seem endless in emerging adulthood. Choices are not certain, and with adult independence, they are optimistic about their future.

Depression and Emotional Problems in the Stages Adolescence

Depression is a mood disorder causing a persistent feeling of sadness for two weeks or more. The National Institute of Mental Health has documented that “3.1 million adolescents aged 12 to 17 in the United States had at least one major depressive episode.” While teenagers are stereotypes as moody, excessive emotional swings can indicate a true emotional problem. Many suffer from depression, anxiety, and eating disorders related to their changing bodies. Female adolescents are more at risk from emotional problems than males. Behaviors such as violence at school, bullying, poor school performance, drinking and drugs, and not having friends are indicative of a deeper problem. An observant, receptive parent or guardian is essential to determine if behavior warrants professional intervention. With loving adults and peers, an adolescent can thrive!  

Supporting Your Child Through the Stages of Adolescence

The stages of adolescence are a stress inducing, emotional period for everyone involved. Parents of adolescents often sense they are in over their heads. Support during adolescence is vital to development, so experts have compiled a list of tips to guide your child through adolescence.

  • Be a role model: Throughout the stages of adolescence, every young person has a role model. Parents should exemplify behavior and values they want their children to display.   
  • Set limits: Adolescents will defy rules and test limits. That is a fact of growing up. However, providing them with structure keeps them safe and shows them that there are consequences for their actions.
  • Communication: Talk out matters of conflict. Your adolescent has to feel comfortable addressing their worries. Find the communication style of your adolescent for open communication.
  • Explain why: Ensure you inform your adolescent why you expect the behavior that you do (i.e. for their safety). Do not settle for averting the point with a “because I said so.” Adolescents must learn to reason and make the connection with their possible decisions.  
  • Listen: Listen to what your adolescent has to say. Your adolescent wants to be heard.  They deserve the same respect.


Age limits and adolescents. (2003). Paediatrics & child health, 8(9), 577-8.

Arnett, J. J. (2013). Adolescence and Emerging Adulthood. Boston, MA: Pearson.

Konrad, K., Firk, C., & Uhlhaas, P. J. (2013). Brain development during adolescence: neuroscientific insights into this developmental period. Deutsches Arzteblatt international, 110(25), 425-31.

Morelli, A.O. & Zupanick, C.E. (N.d.). Adolescent Physical Development. Retrieved from

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