Adolescence

**Adolescence** (from the Latin word *adulescere*, meaning "to grow") is the time of life between childhood and adulthood. It involves important changes in the body, brain, and social life. Adolescence is usually defined as the period from ages 10 to 25. During this time, people go through many changes that prepare them for adulthood.

Today, there are 1.8 billion adolescents in the world, making up a quarter of the global population. Most of them (about 90%) live in low- and middle-income countries, where there are more adolescents due to higher birth rates.

During puberty, which happens between ages 10 and 13, young people rely more on their parents. As they grow older, from 14 to 25, they gain more independence but may also experience emotional and social challenges. Research shows that the brain keeps developing until about age 25, forming new connections. This has helped scientists better understand adolescent growth.

Many things can affect how the brain grows during adolescence. These include genetic and environmental factors, health during pregnancy, nutrition, sleep, medications, and surgeries. Stress, substance use (like caffeine, nicotine, and alcohol), and sex hormones (such as estrogen, progesterone, and testosterone) also play a role in how the brain develops.

## Stages of Adolescence 
### Pre-adolescence/puberty from 10 to 14 years
This phase involves rapid physical growth and sexual maturation, sometimes uneven growth resulting in an odd appearance. Young people often feel tired or worried about being normal, some are shy, stout or modest. Sexual feelings are strong, causing them to often have social contact with the opposite sex, usually in groups.

Puberty is characterized by rapid physical and hormonal development in both boys and girls. This phase is marked by changes aimed at sexual maturation and the development of secondary sexual characteristics.

#### Girls
In girls, puberty usually begins with the development of the breasts, known as thelarche, and the growth of pubic hair. This is followed by the Pubertal spurt, a period of accelerated growth, followed by menarche, the onset of menstruation. Girls may also experience significant emotional and psychological changes due to increased levels of Estrogen and other hormones.

#### Boys
In boys, puberty usually begins with the growth of the testicles and penis, as well as the appearance of pubic hair. The pubertal spurt occurs a little later than in girls and is accompanied by an increase in muscle mass and shoulder size. In addition, there is the beginning of the production of testosterone, which influences the development of characteristics such as voice change and the appearance of facial and body hair.

#### Common aspects
Both sexes may experience a temporary increase in acne and body odor, as well as changes in mood and self-perception. It is common for adolescents in this age group to experience feelings of insecurity and curiosity about their own bodies and how they are changing.''

### Middle adolescence from 15 to 17 years
This phase is marked by continued physical development, excessive activity alternating with extreme lethargy, increased appetite and need for sleep. They are adapting sexually and establishing their sexual identity. Personal feelings of masculinity or femininity may be heightened. They are learning the psychosocial rules surrounding sexual behavior and relating to their partners.

### Late adolescence/emerging adulthood (18–24)
At this stage, physical and sexual maturation is nearly complete, there is a greater acceptance of physical appearance, and a new sense of physical identity is developing. Young people at this stage are defining their identities. Sometimes stable and productive relationships with their partners may occur, and as they are moving from a phase of dependence to a phase of independence, the demands of increasing roles and responsibilities begin to gradually increase as they transition into adulthood.

## References 
## Related pages
* Youth
* Human development (biology)
* Developmental psychology

## Other websites 
* Adolescence -Citizendium .