History of Adolescence in Timeline

Adolescence is the developmental period transitioning from childhood to adulthood, roughly spanning from puberty to the late teens or early twenties. While often associated with the teenage years, its onset and conclusion are variable, influenced by physical, psychological, and cultural factors. Puberty initiates physical changes, and cognitive development continues throughout adolescence. Despite varied scholarly definitions, it's broadly recognized as starting around age 10, extending potentially to 19 or beyond. The World Health Organization defines adolescence as ages 10 to 19.

1904: Publication of 'Adolescence' by G. Stanley Hall

In 1904, G. Stanley Hall's 'Adolescence' was published, marking the beginning of the formal study of adolescent psychology. Hall defined adolescence as the period from ages 14 to 24, viewing it as a time of internal turmoil based on Darwin's evolutionary theory and Freud's psychodynamic theory.

1927: Founding of the Institute of Human Development

In 1927, Jean Macfarlane founded the University of California, Berkeley's Institute of Human Development, which was formerly known as the Institute of Child Welfare.

1931: Initiation of the Oakland Growth Study

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

1932: Data Collection Begins for Oakland Growth Study

In 1932, data collection commenced for the Oakland Growth Study, a longitudinal study examining the development of children in the Oakland area. The data collection continued until 1981.

July 1959: Mark Abrams Identifies the Teenager Consumer

In July 1959, Mark Abrams published "The Teenage Consumer" and identified the emergence of a new economic group called "teenagers" aged 13-25 with unique characteristics such as more money, more discretion, and greater mobility.

1978: Adolescent Weight Gain

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

1980: Adolescent Employment in China

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

1981: Conclusion of Data Collection for Oakland Growth Study

In 1981, the data collection for the Oakland Growth Study, initiated in 1932, concluded, providing researchers with longitudinal data on individuals from childhood into adulthood.

1984: Establishment of the Society for Research on Adolescence (SRA)

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

1986: Hogan & Astone's Definition of Adolescence

According to Hogan & Astone in 1986, adolescence is defined as the transition from child-to-adulthood, including 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's Four-Stage Model for Homosexual Identity Development

In 1989, Troiden proposed a four-stage model for the development of homosexual sexual identity, including 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, defining children as individuals under 18. Almost every country in the world committed to advancing an anti-discriminatory stance towards young people, protecting them against child labor, military enrollment, prostitution, and pornography.

1990: Decline in Adolescent Employment in China

In 1990, less than one fourth of 16-year-olds in China were employed. This marks a significant decrease compared to 1980, likely due to the increased accessibility and perceived importance of formal higher education.

1991: Self-Esteem in Adolescence

In 1991, Mearns noted that contrary to popular belief, there is no empirical evidence for a significant drop in self-esteem over the course of adolescence, though "Barometric self-esteem" can fluctuate rapidly. It was also noted that after the end of a romantic relationship, men and women happen to have a low self-esteem, they are prone to symptoms such as depression and hopelessness.

1991: Adolescent Appearance and Effort

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, unlike children, teens put forth an effort to look presentable.

1995: Gender Differences in Self-Esteem and Mental Health

In 1995, Ustun & Sartorius found that women are twice as likely to experience depression and men are three to four times more likely to commit suicide.

1996: Increase in Computer Usage Among Adolescents

From 1996 to 2006, the amount of time adolescents spent on the computer greatly increased, indicating a significant shift towards digital engagement.

2002: Average Age of First Sexual Intercourse (USA)

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

2005: Brain Development Studies

Studies newer than 2005 indicate that the brain continues to develop in efficiency well past the twenties, suggesting that defining a specific 'point of maturity' in the twenties is somewhat arbitrary, as many important parts of the brain are mature by ages 14 or 15.

2006: Increase in Computer Usage Among Adolescents

From 1996 to 2006, the amount of time that adolescents spent on the computer greatly increased, with online activities such as video games, email, instant messaging, social networking sites, news sources, music, and videos becoming more prevalent.

2008: Sexual Experiences in Adolescence (UK)

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

2009: Parental Influence on Education

In 2009, a study 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: Prevalence of Social Networking Among Adolescents

In 2012, a high proportion of adolescents used social networking sites, with 73% of 12-17 year olds reporting having at least one social networking profile. Additionally, 68% of teens texted every day, 51% visited social networking sites daily, and 11% sent or received tweets at least once every day.

2015: Cyberbullying and Adolescent 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 Students

In 2015, data from the National Institute on Drug Abuse indicated that past year marijuana usage among 8th graders was at 11.8%, and amongst 10th graders at 25.4%.

2018: Marijuana Usage Among Students

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

2020: Impact of Instagram on Adolescent Girls' Body Image

In 2020, 32% of adolescent girls that use Instagram reported feeling worse about their body image after using the platform, indicating a potential negative impact of social media on mental health.