Physical development

During early adolescence – from age 11 to 13 – young teenagers begin to experience rapid changes in body size, shape and physiology (functioning). Hormones – chemicals produced by the body – are largely responsible for these changes.

Puberty commonly begins around this time. However, it can start as early as age 8 for girls and age 9 for boys. Conversely, it may also be delayed in some cases until teens reach middle adolescence. This is part of the normal range of variation in humans and should not be a cause for concern for children or parents.

The brain releases the hormone gonadotropin-releasing hormone (GnRH) that begins the changes of puberty. GnRH signals the pituitary gland, located just beneath the brain, to release into the bloodstream two more hormones that induce pubertal growth. These are the luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Depending on the adolescent’s gender, these hormones target different parts of the body.

In boys, these hormones signal the testicles (male sexual reproductive glands) to begin producing testosterone and sperm. Testosterone is a hormone that is responsible for most of the physical changes in a boy’s body that occur during adolescence. Sperm (the male reproductive cell) is a part of seminal fluid (a whitish fluid) that forms semen, which is ejaculated during sexual arousal.

In girls, FSH and LH stimulate the ovaries (female reproductive glands), which contain eggs, to produce estrogen and progesterone – hormones that prompt the genitals and breasts to mature.

In most girls, the first sign of puberty is breast development and hair growth in the pubic area (on and around the labia), legs and armpits. Sometimes one breast will grow faster than the other, and then breast growth will even out over time. Menstruation begins about two years later on average, although these signs are reversed in some girls. Menstruation is the monthly cycle in sexually mature women that occurs when an egg released from the ovary is not fertilized, causing the mucous membrane lining of the uterus (endometrium) to shed. This results in the discharge of blood from the vagina (the passageway between the lower portion of the uterus and the outside genitals). It is common for girls to have irregular menstrual cycles for several years after starting to menstruate.

Other developmental changes include enlargement of the ovaries, uterus (a pelvic organ that nourishes the fetus during pregnancy), labia (the folds of skin that form the inner lips and outer lips of the vaginal opening) and clitoris (a small organ of erectile tissue located in front of the urethra that is involved in sexual pleasure). Also, a thickening of the endometrium and inner lining of the vagina occurs, resulting in a white, mucus-like vaginal discharge.

In most boys, the first sign of puberty is enlargement of the testicles, followed by the penis (male sex organ), and it is common for one testicle to hang lower than the other. Growth of hair in the pubic area (on and around the penis), legs, armpits, chest and face also occurs. A small amount of breast tissue may develop at this time in some boys. Growth of breast tissue in boys – a condition called gynecomastia – can appear on one or both sides of the chest, and the breast area may feel tender. In most cases, gynecomastia is a temporary condition that often goes away on its own – within a few months to a couple of years – and does not require medical treatment.

Regular use of products containing lavender and tea tree oils (e.g., soap, skin lotions, shampoo, styling products) has been linked to gynecomastia in preteen and teenage boys, according to a recent study published in the New England Journal of Medicine. These oils appear to cause an imbalance in the hormones estrogen and androgen, which control female and male sex characteristics respectively. After use of the products was discontinued by the boys in the study, the condition subsided or resolved within several months. However, more research is needed to confirm this link.

Although most boys begin to get erections during infancy, erections become common during early adolescence. An erection occurs when tissue inside the penis fills up with blood. Erections commonly cause the penis to enlarge and become very hard. Erections can occur when thinking sexual thoughts or sometimes for no reason at all. These can go away on their own or when a boy ejaculates or releases semen (a thick fluid that contains sperm and other secretions) through the urethra (opening at the tip of the penis that also expels urine).

Often during puberty, boys ejaculate at night while sleeping. These are called nocturnal emissions, or “wet dreams.” Nocturnal emissions occur as a result of a buildup of seminal fluid. Nocturnal emissions usually become less frequent as adolescent boys progress through puberty and eventually stop altogether.

For both genders, rapid musculoskeletal growth also begins in early adolescence, but peak growth is generally not reached until middle adolescence (about age 14 to 18). Boys usually peak two to three years later than girls and continue to grow for about two to three years after most girls have stopped. The adolescent growth spurt often begins with enlargement of the hands and feet followed by the arms and legs and finally by the trunk and chest. This may give young adolescents a somewhat awkward appearance temporarily.

Boys lose body fat until their growth spurt is completed and then gradually fat increases. The shoulders commonly grow wider and bodies become more muscular. Muscle mass doubles between ages 10 and 17 in boys. In contrast, girls do not lose body fat. They gradually begin to store fat from about age 6, but the location of storage changes during puberty. More fat is now stored in the stomach, breasts and upper back areas.

The throat and lungs also rapidly enlarge, causing voice changes that are usually more pronounced in boys. Skin changes also occur, such as an increase in oil production by the sebaceous (oil) glands. As a result, many teenagers develop acne. These skin lesions – also called pimples – can develop on the face, upper chest and back. Acne usually becomes less noticeable by the end of adolescence. Skin glands also begin producing chemicals that result in body odor when sweating. This is normal and can be alleviated by bathing more frequently and using plenty of deodorant.  

During adolescence the eyeballs may elongate as well. This often results in nearsightedness (myopia). Patients with myopia usually have good near vision, but poor distant vision. The condition often requires frequent changes in glasses or contact lenses during adolescence. Myopia usually stops progressing as adolescent development is completed. It should be noted that most eyes with nearsightedness are otherwise healthy.

By the time children reach early adolescence, they usually have undergone all their teeth changes – their primary canines and molars have been replaced by permanent canines, premolars and second molars. However, the jawbone (mandible) continues to grow until about age 16. Because of this, some adolescents may need braces or other orthodontic appliances to correct certain dental irregularities, such as not enough spacing between teeth or the reverse, which can occur at this time.

Cognitive development

Early adolescence marks the beginning of more complex cognitive (intellectual) thinking processes in children. Young teens usually begin to move from concrete operational thinking, which is characteristic of middle childhood, to formal operational thinking. This change involves the ability to think in a more complex manner. Teens are now beginning to think about possibilities and to form new ideas and views.

Most importantly, though, they begin to comprehend abstract terms. This means that they can understand complex and hypothetical problems involving abstract concepts, such as mathematical equations like algebra. Generally, children begin to think about the process of thinking at this stage. However, it should be noted that some adolescents acquire this capability later in development.

Although young adolescents can apply formal operational thinking skills to their schoolwork, they often are not able to do the same when it comes to personal dilemmas. This is because when emotions are involved, teenagers may be unable to treat possibilities as real entities. This can affect important decisions, such as whether or not to engage in risky behaviors such as unprotected sex or drug experimentation.

In addition, the way teenagers view moral issues tends to correspond with intellectual development. Most young adolescents tend to view right and wrong in very narrow and rigid terms. At this stage, many adolescents also begin questioning standards of morality handed down to them by authority figures, such as parents, teachers or other adults. They often embrace the behaviors and beliefs of friends. Belonging to a group of peers also allows them to avoid feeling guilty over moral infractions by shifting responsibility from the individual to the group.

Psychosocial development

As a result of the rapid physical changes beginning in early adolescence, teenagers often experience dramatic highs and lows concerning body image and self-esteem. Because puberty does not occur at the same rate for everyone, many young adolescents – who want to be accepted by their peers – tend to worry about their bodies and whether they are developing normally and are attractive.

For instance, boys may worry about whether they are big enough while girls may perceive themselves as overweight, even if they are not. Messages from the media, which typically show unrealistic body types, can influence adolescents’ self-esteem in a negative way. As a result, some boys may experiment with anabolic steroids (prescription drugs that cause tissue and muscular growth) and some girls’ obsession with body image may lead to eating disorders such as anorexia nervosa or bulimia nervosa. These negative behaviors can severely interfere with normal adolescent development, including the lack of a menstrual cycle in girls.

It is normal for young adolescents to begin establishing their individuality by increasing autonomy from family. Common behaviors at this time include avoidance of regular family activities, increased demands for privacy and argumentativeness. Young teens often select adults other than parents as role models and may also develop close relationships with teachers or their friends’ parents.

Being part of a peer group is another way of establishing personal identity for young teens. During early adolescence, peer groups are typically composed of same-sex, non-romantic friendships often in the context of cliques, gangs or clubs such as boy or girl scouts. As adolescents begin to spend more time with friends than family, clothing style and general interests are typically influenced by their peers. This sometimes can lead to familial conflicts as parents struggle with a young adolescent’s budding independence. It should be noted, though, that not all teenagers rebel and not all parents regard their child’s increasing assertiveness as a sign of disobedience. Generally, most teens still aim to please their family even while disagreeing on several issues.

At this time, most young teens are adjusting to the transition from elementary to middle school, which can be stressful. However, in most cases it is a positive type of stress associated with excitement due to academic and social growth.