Adolescent Development
The development of children ages 12 through 18 years old should include expected physical and mental milestones.
During adolescence, children develop the ability to:
- Understand abstract ideas. These include grasping higher math concepts, and developing moral philosophies, including rights and privileges.
- Establish and maintain satisfying relationships.
- Move toward a more mature sense of themselves and their purpose.
- Question old values without losing their identity.
During adolescence, young people go through many changes as they move into physical maturity. Early, prepubescent changes occur when the secondary sexual characteristics appear.
Girls:
- Girls may begin to develop breast buds as early as 8 years old. Breasts develop fully between ages 12 and 18.
- Pubic hair, armpit and leg hair usually begin to grow at about age 9 or 10, and reach adult patterns at about 13 to 14 years.
- Menarche (the beginning of menstrual periods) typically occurs about 2 years after early breast and pubic hair appear. It may occur as early as age 9, or as late as age 16.
- Girls growth spurt peaks around age 11.5 and slows around age 16.
Boys:
- Boys may begin to notice that their testicles and scrotum grow as early as age 9. Soon, the penis begins to lengthen. By age 17 or 18, their genitals are usually at their adult size and shape.
- Pubic hair growth, as well as armpit, leg, chest, and facial hair, begins in boys at about age 12, and reaches adult patterns at about 17 to 18 years.
- Boys do not start puberty with a sudden incident, like the beginning of menstrual periods in girls. Having regular nocturnal emissions (wet dreams) marks the beginning of puberty in boys. Wet dreams typically start between ages 13 and 17. The average age is about 14 and a half years.
- Boys’ voices change at the same time as the penis grows. Nocturnal emissions occur with the peak of the height spurt.
- Boys’ growth spurt peaks around age 13 and a half and slows around age 18.
The sudden and rapid physical changes that adolescents go through make adolescents very self-conscious. They are sensitive, and worried about their own body changes. They may make painful comparisons about themselves with their peers.
Physical changes may not occur in a smooth, regular schedule. Therefore, adolescents may go through awkward stages, both in their appearance and physical coordination. Girls may be anxious if they are not ready for the beginning of their menstrual periods. Boys may worry if they do not know about nocturnal emissions.
During adolescence, it is normal for young people to begin to separate from their parents and make their own identity. In some cases, this may occur without a problem from their parents and other family members. However, this may lead to conflict in some families as the parents try to keep control.
Friends become more important as adolescents pull away from their parents in a search for their own identity.
- Their peer group may become a safe haven. This allows the adolescent to test new ideas.
- In early adolescence, the peer group most often consists of non-romantic friendships. These often include cliques, gangs, or clubs. Members of the peer group often try to act alike, dress alike, have secret codes or rituals, and participate in the same activities.
Adolescents very often have behaviors that are consistent with several myths of adolescence:
- The first myth is that they are “on stage” and other people’s attention is constantly centered on their appearance or actions. This is normal self-centeredness. However, it may appear (especially to adults) to border on paranoia, self-love (narcissism), or even hysteria.
- Another myth of adolescence is the idea that “it will never happen to me, only the other person.” “It” may represent becoming pregnant or catching a sexually-transmitted disease after having unprotected sex, causing a car crash while driving under the influence of alcohol or drugs, or any of the many other negative effects of risk-taking behaviors.
Adolescents become stronger and more independent before they have developed good decision-making skills. A strong need for peer approval may tempt a young person to take part in risky behaviors.
Motor vehicle safety should be stressed. It should focus on the role of the driver/passenger/pedestrian, the risks of substance use, and the importance of using seat belts. Adolescents should not have the privilege of using motor vehicles unless they can show that they can do so safely.
Other safety issues are:
- Adolescents who are involved in sports should learn to use equipment and protective gear or clothing. They should be taught the rules of safe play and how to approach more advanced activities.
- Young people need to be very aware of possible dangers including sudden death. These threats can occur with one time or, especially regular substance use, such as drugs and alcohol.
- Adolescents who are allowed to use or have access to firearms need to learn how to use them properly.
Adolescents may need to be evaluated if they appear to be isolated from their peers, uninterested in school or social activities, or doing poorly at school, work, or sports.
Many adolescents are at increased risk for depression and potential suicide attempts. This can be due to pressures and conflicts in their family, school or social organizations, peer groups, and intimate relationships.
The teenager’s quest to become independent is a normal part of development. The parent should not see it as a rejection or loss of control. Parents need to be constant and consistent. They should be available to listen to the teen’s ideas without dominating the child’s independent identity.
Although adolescents always challenge authority figures, they need or want limits. Limits provide a safe boundary for them to grow and function. Limit-setting means having pre-set rules and regulations about their behavior.
Power struggles begin when authority is at stake or being right is the main issue. These situations should be avoided, if possible. One of the parties (typically the teen) will be overpowered. This will cause the youth to lose face. The adolescent may feel embarrassed, inadequate, resentful, and bitter as a result.
Parents should be ready for and recognize common conflicts that may develop while parenting adolescents. The experience may be affected by unresolved issues from the parent’s own childhood, or from the adolescent’s early years.
Parents should know that their adolescents will repeatedly challenge their authority. Keeping open lines of communication and clear, yet negotiable, limits or boundaries may help reduce major conflicts.
Most parents feel like they have more wisdom and self-growth as they rise to the challenges of parenting adolescents.
Development – adolescent; Growth and development – adolescent.
References
Morelli LW, Rubin DH, Hazen EP. Child, adolescent, and adult development. In: Stern TA, Wilens TE, Fava M, eds. Massachusetts General Hospital Comprehensive Clinical Psychiatry. 3rd ed. Philadelphia, PA: Elsevier; 2025:chap 5.
Holland-Hall CM, Brown MD. Adolescent physical and social development. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 150.
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As children grow into teenagers, their bodies and minds go through many changes. Each stage brings new health needs from nutrition and sleep to emotional well-being and development.
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