Adolescent "illness" is largely classified with either children or adult "illness". The notion of adolescent illness implies distinctive common psychosocial characteristics, rather than symptoms of physical disease or signs of illness¹⁾. The recent economic growth in Korea and the adoption of westernized dietary habits have affected the lifestyle of Korean adolescents accordingly. As the eating habits of adolescents have become increasingly westernized, average weight and height has increased, while a drastic downward trend in pubertal timing has been observed.

Diversified sources of information and constant technological advancements has been providing uncontrolled access of information for everyone. In particular, increasingly available adult content that exposes adolescents to smoking, drinking alcohol, and sexual experiences is progressively more becoming problematic as it creates psychosocial problems. It is important for doctors who specialize in this particular age group to consider and understand the significance of psychosocial factors that are related to risk-taking behaviors for the betterment of patient care and public health.

The average proportion of the adolescent population in developed countries ranges between 13 to 15%²⁾. According to the 2005 Korean population census, the percentage of the population between the ages of 10 and 19 is 13.9% across the entire nation's population, which is consistent with numbers from other developed countries (Fig. 1). The definition of adolescent population used by the National Statistical Office in 2010 has differed at different times; however, overall, the population of people between the ages of 9 and 24 consists of 21.1% of the nation's population and the rate has consistently decreased since 1978.

As Fig. 1 illustrates, the notable difference between the Korean population and those of other developed nations is that the pediatric population (age, 0 to 9 years) comprises 11.8% of the total population, which is less than the total population of adolescents, while the pediatric population (age, 0 to 4 years) has decreased to 5.1%. This figure indicates that the adolescent population comprises the majority of the general patient populations of pediatricians, an important factor to consider for future implementation of adolescent health solutions.

According to the National Statistical Office of Korea, the mortality rate of the adolescent population between the ages 10 to 19 decreased to 22.2 per 100,000 in 2009 from 38.2 in 1999. However, it showed an increment of 5.5% from the previous year. The major cause of death in the adolescent population is suicide, followed successively by transport accidents, and malignant neoplasm (Fig. 2)³⁾.

From 1999 to 2008, the major causes of death in the adolescent (age, 10 to 19 years) population were, in order, transport accidents, suicides, and malignant neoplasm. The change in the major cause of death from transport accidents to suicide appears to be due to an increased rate of suicides. In 2008, the suicidal rate per 100,000 was 4.6, but increased to 6.5 people per 100,000 in 2009.

The primary causes of adolescent suicides are school-related problems such as stress from overwhelming academic responsibilities, mental health problems, lack of social support, and other socioeconomic issues.

The average height of a 12-year old Korean boy in 2008 was 158.1 cm, a 4.5 cm increase from 10 years ago (153.6 cm in 1998). The average weight has also increased by 4.9 kg, from 45.0 kg in 1998 to 50.8 kg in 2008.

There have been changes not only in physical indices but also in sexual maturation based on the Sexual Maturity Rating (SMR). In 1994, the average Korean female adolescent's first pubertal change, breast budding (SM2), occurred at the age of 11 years. Development of pubic hair (SMR2) took place at an average age of 12.9 years. For male adolescents, the first growth of testes (SMR2) occurred at an average age of 12.7 years, 1.7 years later than female adolescents, and development of pubic hair (SMR2) occurred at an average age of 13.2 years⁴⁾. These figures were similar to British adolescents, where breast budding occurs at an average age of 11.2 years, and the first growth of the testes is at the age of 11.6 years⁵⁾. These numbers illustrate the similarities between Korean statistics and those from developed western countries, with exception that Korean male adolescents begin pubertal development 1.1 to 1.5 years later than western male adolescents.

The current median age of menarche in Korean adolescents is 12.8 years, 1 year earlier in 1982⁶⁾. Comparisons with other studies show that, in the last 10 year period, menarche has occurred earlier each year. In 2009, the mean age of menarche was 12.4⁷⁾ this trend of menarche occurring at an early age was evident from results presented by Kim et al.⁸⁾ in 2010.

The increase in the rates of sexual experience, and decrease in the average age of first sexual experience, is causally associated with earlier pubertal changes.

Due to the recent economic growth in Korea and improvement in diet, the problems of excessive caloric intake, nutritional unbalance, and lack of exercise have intensified throughout the population, there has been a consistent increase in the number of overweight or obese individuals in the population.

Korean adolescents often face excessive competition for school entrance exams, leading to an increase in the frequency of sedentary activities that prevents physical activity and causes significant adolescent health risks. In addition, their busy daily schedule causes irregular dietary habits and increased consumption of fast foods, and carbonated drinks, resulting in inadequate nutrition and lack of a healthy diet for adolescents. Mental instability from excessive academic stress is another factor that may cause adolescent weight gain leading to obesity, which negatively affects the quality of life and is a cause of early death when obesity continues through adult life.

The increasing number of adolescents faced with mental health problems is a growing problem worldwide. In the state of Minnesota in the U.S., 57% of the adolescent population faced intervention based on mental health issues at least once in 2006¹⁴⁾. Further, 10 to 20% of adolescents are faced with mental health problems or disorders and their mental disorders might lead to the onset of adult depression¹⁵⁾.

In case of Korean adolescents, an excessively competition-oriented education environment, sudden changes in socio-cultural values, and the introduction of foreign cultures are constantly preventing them from building firm personal values and independent thinking. Depression, drug addiction, smoking, wrongdoing, bullying, social isolation, addiction to the internet or computer games and maladjustment behaviors are becoming obvious social problems among Korean adolescents. According to the Seoul Child and Adolescent Mental Health Center, 35.8% of 2,664 participating adolescents have exhibited mental health problems¹⁶⁾.

According to statistics from the Ministry of Health & Welfare, 43.2% of Korean adolescents are faced with severe stress while the corresponding number for adults is 28.9%. It was discovered that female adolescents faced more stress than male adolescents. This study also revealed that 37.5% of participants had experienced severe depression for at least 2 weeks during the previous 12-month period. Compared to 26.1% of U.S. high school students experiencing depression, more Korean students exhibited symptoms of depression7,¹¹⁾.

Suicide: Previous research findings suggest that hopelessness, daily stress, alienation, depression, lack of self-esteem, lack of self-identity, inadequate social support, and psychological construct are all causative factors for suicide¹⁷⁾. In 2006, 32.6% of Korean adolescents had thoughts of suicide and 3% (135 individuals) admitted to attempting suicide¹⁸⁾. Another study revealed that 19.1% (15.2% of males and 23.5% of females¹⁹⁾ of Korean adolescents had thoughts of suicide in the past 12 months and 4.6% had actually attempted suicide.

The recent increase in adolescent use of alcohol, tobacco and other illicit substances poses a health threat for adolescents. A survey in 2009 revealed that, Korean adolescents admitted to using drugs and other illicit substances for personal reasons other than for the treatment of illness. The list of abused substances includes analgesics (49.3%), cough and cold remedies (43.3%), alcohol (37.7%), tobacco (17.6%), tranquillizers and sleeping pills (4.8%), stimulants (2.6%), medicine for Attention-deficit hyperactivity disorder (2.5%), diuretics and diet pills (1.7%), and hallucinogenic inhalants (1.3%)¹⁹⁾.

As the Korean drinking culture is generous and hospitable, early adolescent drinking habits pose a serious health treat, cultivate unhealthy drinking habits, and increase the risk of inhalation of super-adhesive agents, leading to deviant behavior. The rate of cigarette smoking among Korean adults is among the highest of the nations in the Organization for Economic Co-operation and Development. As the adolescent rate of cigarette smoking is closely related to the adult rate of cigarette smoking, it is important to note the relationship between the two figures.

Smoking during the adolescent period causes delayed physical growth and respiratory disease, and is harmful for the development of mental health. Smokers are more likely to experience depression or harbor thoughts of suicide than nonsmokers. They are also often faced with higher stress levels, causing and increased occurrence of depression and, anxiety disorders²⁰⁾. Past smoking experiences increase the likelihood of future smoking in adolescents, depending on the smoking status of parents or friends²¹⁾.

Adolescent sexuality issue is a growing problem as the number of adolescents who are sexually experienced before marriage is increasing. Their limited knowledge of contraception and of sexual matters, and attitudes, cause unintended pregnancy and sexually transmitted diseases (STD). These unintended pregnancies and STDs can cause physical as well as psychological and social damage in adolescents.

During the adolescent period, they undergo rapid physical, emotional and, cognitive development, including the establishment of lifestyle and habitual routines that strongly influence adult health life. Therefore, it is important to build a healthy lifestyle and acquire a proper view of health during this period. If healthy habits and a proper view of health are not established, it could lead to risk-taking behaviors. Since such behaviors are a major cause of adolescent mortality and morbidity, these issues must be addressed with much care.

The recent rapid economic growth, and the earlier onset of physical, sexual, and psychological maturation among adolescents compared to many years ago, influences their health status. The incidence of weight increase, sexual maturation, drinking alcohol, smoking, sexual experiences, and other risk-taking behaviors is increasing, and adolescents experience these factors earlier. Therefore it is important to note that the risk-taking behaviors of adolescents are caused by individual psychosocial factors.