Epidemiology of substance use in adolescence: prevalence, trends and policy implications

Abstract

This paper reviews the epidemiology of substance use among adolescents. There is a public health imperative in all countries to assess the population rates of tobacco, alcohol and illicit drug use among adolescents. In addition, monitoring trends over time may reflect the net effects of activities and programs carried out to prevent adolescent substance use. School based surveys provide prevalence estimates of substance use, but do not capture street and homeless youth and other high risk adolescents not found in the school environment. Overall, the results of this review suggest that tobacco, hazardous alcohol use, and most categories of illicit drug use have shown consistent increases in prevalence since about 1990 in most developed countries, for school-based adolescents, suggesting that the substance use problem among adolescents remains unsolved. These trends are remarkably similar across substance use behaviours, and among most developed countries, although limited data has emanated from adolescents in the developing world. Interventions to reduce or prevent substance use have shown mixed results, with those focusing on the adolescents’ social environment showing the most promise. Broader public health approaches, including the linkage to community-wide prevention, and greater enforcement or regulatory and legislative approaches to tobacco and alcohol access are future directions for research and practice.

Introduction

Tobacco, alcohol and illicit drug use are among the most important global public health problems, with their genesis in adolescence. Their long-term adverse health consequences are well documented, but short-term outcomes among adolescents are important and include associations with injury, violence and suicide, teenage pregnancy, sexually transmitted diseases, and adverse mental health (Sells and Blum, 1996). The main emphasis of this paper is to describe the prevalence of usage in adolescent populations, to indicate what is known of recent trends, and to appraise the effectiveness of prevention programs aimed at reducing the initial use and maintenance of tobacco, alcohol and other drug use. The paper is divided into five sections: (i) introduction, (ii) epidemiological issues of study design and measurement, (iii) prevalence and recent trends in use, (iv) interventions to reduce substance use, and (v) public health and policy implications. The focus is on describing use and misuse in the whole adolescent population, rather than an emphasis upon clinical populations who are more likely to be misusing substances. The need for and effects of treatment services are dealt with elsewhere in this issue. This paper summarises prevalence rates of usage, recent trends, and the effectiveness of interventions addressing substance use. A detailed exploration of the risk factors associated with tobacco, alcohol and illicit drug use is provided elsewhere in this issue.

Adolescence is a period of cognitive, biological, physiological and psychological transition, often described as occurring between 10 and 19 years of age (Crockett and Petersen, 1993). The psychological and social transitions of adolescence lead to the need for independence, autonomy, identify formation and acceptance by peers. All of these contribute to the risk taking behaviours of adolescence, of which substance use is the most damaging (Franzkowiak, 1987; Fergusson and Horwood, 1995). The context of substance use includes the social, school and domestic environments for each adolescent, as well as the relevant regulatory and legislative environments present in the community. Detailed consideration of each of these environments is needed to understand and explain the prevalence and trends in substance use. The similarities among countries are far greater than their differences; across the world, recent trends since 1990 have suggested increases in many dimensions of adolescent substance use. The overall efforts aimed at tobacco and alcohol control have not been successful for all adolescents, and greater efforts are required. To this end, the epidemiological tasks of regular monitoring of prevalence, trends and possible determinants is required.

This paper uses the term ‘substance’ to refer to tobacco, alcohol, marijuana, cocaine, amphetamines, hallucinogens, inhalants, and steroids. Except for tobacco and alcohol, these substances are generally regarded as illicit drugs. A wide variety of terms are used to define adolescent substance use. These terms include: substance abuse, substance misuse, substance dependence, dependent use, harmful use, hazardous use, experimental use, problem use, addiction, alcoholism, chemical abuse, and chemical dependence. The most widely used approach in defining and conceptualising problematic substance use is the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association, 1994). The DSM-IV classifies individuals with substance use problems into two distinct categories–substance abuse and substance dependence. Abuse implies maladaptive use leading to failure to fulfil work school or social responsibilities. Dependence is a more severe form of abuse, often involving increasing use of a substance, high tolerance, and a strong desire to use a substance despite significant clinical and social impairments.

Although the two categories of the DSM-IV contain extensive diagnostic criteria of substance use problems, the definitions exclude individuals who are engaged in experimental or recreational use–the most common pattern of use in the community. The focus of this paper is on substance use at the population level, and not on pathological substance use. This paper uses the term ‘substance use’ to denote use that may range from experimental to persistent or dependent use, while the term ‘substance misuse’ is employed specifically to refer any level of use that is harmful to the user or others. ‘Misuse’ encompasses a wider spectrum of problematic or harmful use. These terms are consistent with the conceptualisation of substance use and misuse, as broadly defined by the DSM-IV and the United Kingdom (UK) HAS report (Health Advisory Service, 1996). The adoption of such terms allows for the inclusion of young people with low or episodic substance use. In this regard, this paper acknowledges that tobacco and illicit drug use is a significant public health problem worldwide, and any pattern of use of these substances by adolescents is potentially hazardous. The definitions of alcohol use and misuse, however, usually depend on a society’s acceptance or tolerance of such use. Thus, alcohol misuse is defined in this paper as consuming five or more alcoholic drink on at least one occasion (binge drinking), as defined by other researchers (Cooney et al., 1994; Johnston et al., 1996).

Cigarette smoking represents the major cause of morbidity and premature mortality in developed countries (Taylor, 1993; Gold et al., 1996). Over the past 30 years, public health initiatives have been successful in reducing adult smoking rates in developed countries, but the relatively high, and recently increasing smoking prevalence rates among young people remains a challenge (Gilpin et al., 1994; US Department of Health and Human Services, 1994; Hill et al., 1995). Tobacco use is problematic as almost all use starts in adolescence, with typical initial experimentation between 11 and 15 years of age (Yu and Williford, 1992).

This leads to regular use (and addiction) within 2–3 years while still in school (Best et al., 1988; Pierce and Gilpin, 1996). The level of consumption and the duration in which young people continue as regular smokers depend on the period when smoking experimentation and uptake occur. Tobacco is also of concern as it is thought, along with alcohol misuse, to lead to other drug use; this is known as the ‘gateway’ effect, and has implications for other drug prevention programs (Torabi et al., 1993; Lindsay and Rainey, 1997).

Nearly all school students in developed countries report some experience with alcohol before the completion of high school, with over a third reporting hazardous use at least once (Sells and Blum, 1996). Although many young people may drink less regularly than adults, they tend to engage in heavier drinking in a single session. Drinking to the point of intoxication is of concern because of the associations between alcohol consumption and road accidents, suicides, homicides, and violence (Hewitt et al., 1995; King et al., 1996b). Hazardous bouts of alcohol use have also been related to increased risks of contracting sexually transmitted diseases (STDs), human immunodeficiency virus (HIV) infection, teenage pregnancy, and poor school performance (Lowry et al., 1994; King et al., 1996b; Shrier et al., 1996).

The most prevalent illicit drug used is marijuana. In addition, legal substances used in hazardous ways are included here, including the inhalation of solvents, and the inappropriate use of prescribed medications such as sedatives, minor tranquillisers, and anabolic steroids. Although low in prevalence, illicit drug use has the potential to impact upon health and social functioning in young people. Public health approaches to reducing the adverse health and social harms associated with illicit drug use are of particular importance due to the potential for the spread of HIV, hepatitis and other infectious diseases amongst intravenous illicit drug users. Despite a decline in prevalence throughout the 1980s, increases in the use of most illicit drugs in adolescence has been a worldwide phenomenon since 1990 in many countries (Centers for Disease Control and Prevention, 1991a, Centers for Disease Control and Prevention, 1991b, Centers for Disease Control and Prevention, 1991c, Centers for Disease Control and Prevention, 1991d; Cooney et al., 1994; Kann et al., 1996).