Adolescence is an important developmental stage during which new activities, including social, emotional, and sexual relationships, are experienced, and many lifestyle habits are established. Unhealthy behaviors such as drinking, smoking, and illicit drug use commence more commonly during adolescence than at other developmental stages [1]. These behaviors are closely related to increased morbidity and mortality [2, 3]. Teenage drug use is tightly associated with severe substance use problems, psychiatric disorders, and criminal behavior in young adulthood [4–6].

Protective factors against substance use include greater potential for resilience [7, 8], religiosity [9, 10], and effective parental monitoring [11–14]. Risk factors for drug experience include drug use by parents and friends [15, 16], low academic performance [17, 18], low self-esteem [19], depressive symptoms [20], history of stressful events [21], and early use of alcohol and cigarettes [22, 23].

Mental health is another important factor. Studies of data collected from the Global School-Based Health Survey have examined the association between risk behaviors (alcohol, tobacco, and drug use) and mental health, feelings of solitude, social isolation, and insomnia, and have found a significant association between mental health and substance use among adolescents [24]. This association between psychiatric problems and substance use may be bidirectional; psychoactive substances may be used as “self-medication” by patients with psychiatric disorders. For example, alcohol may be used to induce sleep and temporarily alleviate feelings of anxiety and depression [25]. A study of 1285 subjects aged 9 to 18 years found that regular cigarette smoking, alcohol consumption, and illicit substance use in the previous year were each independently associated with an elevated likelihood of diagnosis with psychiatric disorders (i.e. anxiety, mood, or disruptive behavior disorders) [26]. Bipolar disorder and depression are important risk factors, and they often precede substance use in childhood and adolescence [27, 28]. In contrast, substance use is associated with increased risk of psychopathology in adolescents and young adults. The longitudinal Mater-University of Queensland Study of Pregnancy (MUSP) found that adolescent drinking predicted poly-substance use and mental health disorders in young adulthood [29]. An Australian review found that frequency of cannabis use is positively associated with severity of anxiety disorders and depressive symptoms in young people [30].

Historically, available data have shown that illicit drug use is substantially lower in South Korea than in many other countries including the United States and Japan [31]. However, since the 1990s, drug abuse has expanded in Korean society. Students studying abroad have played a key role in expanding the variety of available drugs, from LSD, Ecstasy, and other new drugs, to potent analgesics [32]. According to the data collected by law enforcement agencies, there was an increase in the number of teenage offenders who violated the Harmful Chemical Law from 476 in 2008 to 1127 in 2012. Because of the rapid increase in illicit drug use among Korean adolescents, there is a need for research to identify the correlates of drug use, which are not well-known in this population.

Development of preventive approaches that aim to reduce or eliminate risk requires identification of substance use risk factors. In this study, we investigated prevalence as well as the socio-demographic correlates and associated psychological problems of substance (alcohol, tobacco, and illicit drug) use in a nationally representative sample of Korean adolescents.

This is the first nationally representative study of adolescent substance use to include illegal drugs as well as alcohol and tobacco in South Korea. Frequencies of alcohol use and smoking among Korean adolescents were similar to those among adolescents in other countries [34–36]. However, frequency of illicit drug use among Korean adolescents was observed to be much lower than among adolescents in other countries [20, 22, 24, 36, 37].

Inhalants and solvents was the most common drug class used for the first time. These substances may be chosen due to their relative availability, low cost, and rapid onset of effect [38]. Individuals using glues or thinners for the purposes of hallucination and stimulation, or selling these substances for these purposes, may be charged under the Harmful Chemical Control Law in South Korea [32]; however, butane gas, adhesives, and glues containing toluene are sold widely and can be purchased easily over the counter. Inhalant use may be followed by other illicit drugs, as adolescents expand the variety of drugs used.

Consistent with previous studies in other countries [39, 40], males and older adolescents more commonly used substances compared to females and younger adolescents. Living with parents has a protective effect against substance use, while low parental education level and low socio-economic status was associated with substance use. These results are consistent with previous studies that have reported the importance of family supervision and living with parents to reduce the likelihood of substance use [11–14].

The association between low academic achievement and substance use may be bidirectional. Students may use substances to cope with their anxiety over academic failure [18, 41]. Moreover, poor academic performers may be more likely to skip school, have disciplinary problems, and engage in deviant behaviors than high achievers, and this may create a social structure that encourages substance use [18, 42]. In contrast, substance use may be a contributory factor to academic difficulties, via skipping class and reduced academic motivation [41, 43]. A third explanation is that substance use and failing academic performance are the result of shared factors, such as a general propensity for deviance [44]. As we did not obtain relevant information about temporality, no inferences about causality are possible in this study.

Previous studies have reported that alcohol, tobacco, and illicit drug use and sexual risk-taking are highly comorbid [45], and that alcohol and tobacco are used first, followed by illicit drugs [23]. Consistently, we found inter-relationships between sexual activity and use of alcohol, tobacco, and illicit drugs.

Associations between substance use and severe stress, depression, and suicidality were consistent with previous studies in other countries [20, 21, 46]. Adolescents may initiate or accelerate substance-use behaviors as a way to cope with their stress, negative mood, and suicidal ideation. Another possible explanation is that their perceived stress and negative mood may be elicited as symptoms of withdrawal from the drugs, which in turn leads to repetitive use of the drugs. Because of such interactive or circular relationships, multifaceted approaches that treat or prevent adolescent depression and/or suicidality, while dissuading adolescent involvement in substance-use behaviors, may both improve their mental health and reduce risky behaviors.

The limitations of this study include that depressive mood and perceived stress was measured using one item each, rather than with standardized multi-item measures. This may limit the validity of measurements of these variables. Additionally, the prevalence of substance use and sexual activity might be underestimated because this survey was conducted in school and did not include adolescents who were not attending school, a high-risk group for delinquent behavior [44, 47]. Moreover, social desirability may have biased the survey results. Although the survey was anonymous, drug use may have been underreported due to reluctance to disclose illegal drug use. Additionally, due to inadequate statistical power, the present study was unable to examine correlates of use of each type of drug. Furthermore, frequency of substance use, and sex risk level (e.g. unprotected sex; sex with multiple partners), were not assessed in this study. Finally, as we did not obtain relevant information about temporality, inference of a causal relationship between substance use, psychological problems, and risky behavior is impossible. However, the strength of the present study is its inclusion of data from 72,060 adolescents from a nationally representative sample in South Korea, which improves external validity of the study results.

Even within the context of these limitations, the results of the present study indicate that the use of substances (alcohol, tobacco, and illicit drugs) among Korean adolescents is associated with socially disadvantaged families, psychological problems, and risky behavior. Health education including dependency prevention programs is needed for these high risk groups in South Korea. Future prospective studies are required in order to identify casual relationships among substance use, psychopathology, and suicidality.