History of Adolescence in Timeline

Adolescence is a transitional phase between childhood and adulthood, generally spanning from puberty through the teenage years, though its precise duration is debated. Physical growth and cognitive development continue during this period. While age serves as a rough marker, definitions vary, with some extending the period from as early as 10 to as late as 30. The World Health Organization defines adolescence as the period between the ages of 10 and 19.

1904: Publication of G. Stanley Hall's Adolescence

In 1904, G. Stanley Hall's "Adolescence" was published, marking the formal beginning of adolescent psychology as a field of study. Hall defined adolescence as the period from ages 14 to 24, viewing it as a time of internal turmoil.

1927: Founding of the Institute of Human Development

In 1927, Jean Macfarlane founded the University of California, Berkeley's Institute of Human Development, formerly the Institute of Child Welfare. The institute initiated studies of healthy development.

1931: Initiation of the Oakland Growth Study

In 1931, Harold Jones and Herbert Stolz initiated the Oakland Growth Study to study the physical, intellectual, and social development of children in the Oakland area.

1932: Data Collection Began for Oakland Growth Study

In 1932, data collection began for the Oakland Growth Study, gathering longitudinal data on individuals that extended past adolescence into adulthood. The study was initiated by Harold Jones and Herbert Stolz in 1931.

July 1959: Mark Abrams publishes The Teenage Consumer

In July 1959, Mark Abrams published "The Teenage Consumer", identifying the emergence of a new economic group aged 13–25, coining the term "teenager" to describe this group.

1978: Adolescents experience significant weight increase

In 1978, Marshall noted that adolescents experience a significant increase in weight during puberty, with the weight gained during this period constituting nearly half of an individual's adult body weight.

1980: Adolescent Employment in China

In 1980, half of all 16-year-olds in China were employed, marking a significant level of adolescent participation in the workforce.

1981: Conclusion of data collection for the Oakland Growth Study

In 1981, data collection concluded for the Oakland Growth Study, initiated in 1931 by Harold Jones and Herbert Stolz. Researchers were able to gather longitudinal data on individuals that extended past adolescence into adulthood.

1984: Formation of the Society for Research on Adolescence

In 1984, the Society for Research on Adolescence (SRA) became the first official organization dedicated to the study of adolescent psychology.

1986: Markers of the Transition from Child-to-Adulthood

According to Hogan & Astone (1986), the transition from child-to-adulthood can include markers such as leaving school, starting a full-time job, leaving the home of origin, getting married, and becoming a parent for the first time.

1989: Troiden proposed a four-stage model for homosexual identity development

In 1989, Troiden proposed a four-stage model for the development of homosexual sexual identity. The stages include sensitization, identity confusion, identity assumption, and commitment.

1989: Advent of the Convention on the Rights of the Child

In 1989, the Convention on the Rights of the Child was established, committing almost every country in the world (except the U.S. and South Sudan) to advance an anti-discriminatory stance towards young people, including protecting them against child labor, military enrollment, prostitution, and pornography.

1991: Mearns study on self-esteem and depression

In 1991, Mearns published a study stating that women are twice as likely to experience depression after a romantic relationship ends.

1991: Adolescents pay attention to their appearance

In 1991, it was observed that adolescents pay close attention and give more time and effort to their appearance as their body goes through changes.

1995: Ustun & Sartorius study on self-esteem and suicide

In 1995, Ustun & Sartorius published a study stating that men are three to four times more likely to commit suicide after a romantic relationship ends.

2002: American study on average age of first sexual intercourse

In 2002, an American study found that those aged 15–44 reported that the average age of first sexual intercourse was 17.0 for males and 17.3 for females.

2005: Brain efficiency changes beyond the twenties

Studies newer than 2005 indicate that the brain is changing in efficiency well past the twenties. Maturity is hard to define, with many brain parts mature by 14 or 15.

2008: YouGov survey on first sexual experience

In 2008, a YouGov survey for Channel 4 revealed that 20% of 14−17-year-olds surveyed in the United Kingdom had their first sexual experience at 13 or under.

2009: Study on parental influence on education

In 2009, a study conducted by Adalbjarnardottir and Blondal showed that adolescents at the age of 14 who identify their parents as authoritative figures are more likely to complete secondary education by the age of 22.

2012: Social Networking Among Adolescents

As of 2012, 73% of 12–17 year olds reported having at least one social networking profile. 68% of teens texted every day, half (51%) visited social networking sites daily, and 11% sent or received tweets at least once every day. 34% of teens visited their main social networking site several times a day.

2015: Cyberbullying and Depression

A 2015 review reported that "adolescents lack awareness of strategies to cope with cyberbullying, which has been consistently associated with an increased likelihood of depression."

2015: Marijuana Usage Among Adolescents (2015)

In 2015, data from the National Institute on Drug Abuse showed that past year marijuana usage among 8th graders declined from 11.8%. Usage among 10th grade students was 25.4% and 34.9% among 12th graders.

2018: Marijuana Usage Among Adolescents (2018)

In 2018, data from the National Institute on Drug Abuse shows that past year marijuana usage among 8th graders declined to 10.5%; among 10th grade students, usage rose to 27.50%; and among 12th graders, usage rose slightly to 35.9%.