Young adult (psychology)
According to Erik Erikson's stages of human development, first enumerated in Childhood and Society (1950) a young adult is a person between the ages of 18 and 40, whereas an adolescent is a person between the ages of 12 and 17. The young adult stage in human development precedes middle adulthood. A person in the middle adulthood stage is between the ages of 40 and 65. In maturity, a person is 65 years old or older.
Biological function and physical performance reach their peak from 20-35 years of age, waning after 35. Strength peaks around 25 years of age, plateaus through 35 or 40 years of age, and then declines. Flexibility also decreases with age throughout adulthood. However, there are large individual differences and a fit 40-year-old may outcompete a sedentary 20-year-old. 
Women reach their peak fertility in their early 20s.  Assuming unprotected intercourse with a man of the same age, women aged 19-26 have about a 50% chance of becoming pregnant during a given menstrual cycle, compared with 40% in the 27-34 age group and below 30% for women 35-39. 
In developed countries, mortality rates for the 20-40 age group are typically very low. Men are more likely to die at this age than women, particularly in the 18-25 group: reasons include car accidents and suicide. Mortality statistics among men and women level off during the late twenties and thirties, due in part to good health and less risk-taking behavior. 
In sub-Saharan Africa, HIV/AIDS has hit the early adult population particularly hard. According to a United Nations report, AIDS has significantly increased mortality of between ages 20 to 55 for African males and 20 to 45 for African females, reducing the life expectancy in South Africa by 18 years and in Botswana by 34 years. 
According to Erikson, the young adult stage involves the personal need for intimacy and sex. Failure to achieve this need results in isolation, which is avoided, and as a result the young adult strives for love and compassion. The young adult learns that love and compassion may get him what he wants.
In modern societies, young adults in their late teens and early 20s encounter a number of issues as they finish school and begin to hold full-time jobs and take on other responsibilities of adulthood. In the late teens and early 20s, young adults become individuals and will set themselves apart. Self becomes the main reliance. Young adults will strive to become independent from parents, take responsibility for themselves and make their own decisions. During the young adult stage, mainly the majority think in a more mature manner and take issues more seriously. They focus on the construction of a better future. Adolescents are generally regarded as naïve and inexperienced, but are expected to grow into mature adults in their 20s. Young adults in this stage of human development learn value in both tangible and intangible objects. Their relationships with their parents and older adults change. However, in many cases, young adults and adolescents have enormous talent that can, in cases, outstrip some adults' talents. In many cases, problems such as lack of time (schooling and other commitments) and lack of money can arrest the adolescent's development in terms of intellectual and talent growth.
After the upheaval of the early 30's, the middle to late 30's (roughly ages 34-39) are often characterized by settling down. People in their 30's may increase the financial and emotional investments they make in their lives. Many have been employed long enough to gain promotions and raises. They often become more focused on advancing their careers and gaining stability in their personal lives. They may have started a family.
- Martin Briner, Erik Erikson page, 1999, on Briner's site about learning theories, USMA Department of Mathematical Sciences, Center for Assessment and Program Evaluation (CAPE), United States Military Academy at West Point. Accessed 24 November 2006.
- Shephard, Roy J. (7 March 1998). "Aging and Exercise". Encyclopedia of Sports Medicine and Science. T.D.Fahey. Retrieved 2007-06-26.
- http://www.nlm.nih.gov/medlineplus/ency/article/001191.htm Infertility] Medline Plus Medical Encyclopedia Update Date: 5/15/2006 Updated by: Melanie N. Smith, M.D., Ph.D., Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Boston, MA. Review provided by VeriMedHealthcare Network.
- http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2002/04/30/MN182697.DTL Study speeds up biological clocks: Fertility rates dip after women hit 27] Carl T. Hall, San Francisco Chronicle April 30, 2002
- "Life Expectancy Profiles". BBC. 6th June 2005. Retrieved 2007-06-26. Check date values in:
- "UK cancer mortality statistics by age". Cancer Research UK. May 2007. Retrieved 2007-06-26.
- "Cancers at a glance". Cancer Research UK. May 2007. Retrieved 2007-06-26.
- Ngom, Pierre and Clark, Samuel (18 August 2003). "Adult Mortality In The Era Of HIV/AIDS: Sub-Saharan Africa" (pdf). Population Division, Department of Economic and Social Affairs, United Nations Secretariat. Retrieved on 2007-06-26.
|Stages of human development