Epidemiology of Substance Abuse

Denise B. Kandel, Ph.D., Chief of Psychiatric Research
Pamela Griesler, Ph.D., Research Scientist IV
Christine Schaffran, M.S., Research Scientist III

Overview
The department investigates the natural history of drug involvement, the risk factors and consequences of drug abuse and the comorbidity of substance abuse with dysfunctional behaviors and psychiatric disorders among adolescents and adults. Cigarette smoking and nicotine dependence represent a major focus of our research activities. Our program of research generates hypotheses to be tested in the laboratory and illustrates the important contributions that epidemiological investigations of substance use can make to biological research.

The following areas continue to be emphasized: (1) the natural history of nicotine dependence; (2) ethnic differences in the etiology of adolescent smoking; (3) developmental stages of involvement in drugs; (4) the intergenerational transmission of substance use; (5) the impact of maternal smoking in pregnancy and postnatally on offspring smoking and behavior problems. Investigations are based on multiple general population samples, including longitudinal samples and relational samples of matched parent-child and child-best friend pairs.

Our major efforts this past year have focused on implementing a multifactorial longitudinal investigation of the transition from experimental smoking to daily smoking and nicotine dependence in adolescence. This program of research is supported by the National Institute on Drug Abuse, the National Cancer Institute and the American Legacy Foundation.

The goals of the research are to identify risk and protective factors that can either promote or prevent the progression to daily smoking and nicotine dependence among youths, and to examine ethnic and gender differences in these processes, and to contribute to the development of more effective school-based smoking and substance use prevention programs. The study will identify the periods in adolescence when interventions would have optimum benefits and the risk factors that should be the target of interventions.

A two-phase research design will be implemented in order to identify 6th through 10th graders who will be followed over a two-year period. In Phase I, school surveys will be implemented. Smoking and non-smoking students will be selected for participation in Phase II of the study, a longitudinal follow-up. Three annual household interviews will be conducted with students and their mothers, and two additional semi-annual interviews with students. Risk and protective factors will be assessed. At each interview, a saliva sample will be collected to permit determination of nicotinine levels. These will be used not only to validate the self-reports of smoking but to predict persistence of smoking and progression to regular smoking and nicotine dependence.

Selected Findings
Ethnic Differences in Predictors of Smoking Ethnic differences in predictors of smoking were examined in a national longitudinal sample of mother and child dyads. There are more common than specific familial, social and behavioral predictors of initiation and persistence of smoking among youths of different ethnicity. Across ethnic groups, maternal smoking, peer pressure to smoke and problem behavior are risk factors for smoking initiation; problem behavior and low academic competence are risk factors for smoking persistence. Interpersonal factors are more important for onset of smoking than persistence; intrapersonal factors are more important for persistence.

The Natural History of Nicotine Dependence The natural history of nicotine dependence was examined in a national sample from retrospective data on age of onset into smoking, rates of daily smoking, age of onset into daily smoking, and rates of nicotine dependence. Early smokers are more likely to progress to daily smoking and daily smokers are more likely to be dependent than non-daily smokers. However, progression to daily smoking is slower for those who onset early (below age 15) than those who onset at a later age.

Developmental Stages of Drug Involvement Dr. Kandel edited a volume on the Gateway Hypothesis which was published by Cambridge University Press in the spring of 2002. The Gateway Hypothesis postulates that there is a regular sequence of involvement from cigarettes and alcohol to marijuana and to other illicit drugs. The volume synthesizes what is currently known about sequences and stages of drug use in different population groups, specifies the effects of drug prevention efforts on sequences of involvement, analyzes the advantages of different statistical approaches for identifying stages of involvement, and presents what is known about drug progression from animal models and the neurobiology of addiction.

The best fitting progression models are slightly different for men and women, with alcohol playing a more important role in the progression for men than for women. For women, the best fitting model of progression is one in which either alcohol drinking or cigarette smoking must precede marijuana use, marijuana use must precede cocaine use, marijuana use must precede heroin use, and cocaine use must precede heroin use. For men, the best fitting model is one in which either alcohol or cigarette smoking must precede marijuana use, alcohol drinking and marijuana use must precede cocaine use, and alcohol drinking, cigarette smoking and marijuana use must precede heroin use. The same basic model (male) fits all three ethnic groups. Higher position on the scale of drug progression is related to greater dependence on lower stage drugs.

Predictors of Dependence on Various Drug Classes The predictors of dependence on alcohol, cigarettes, marijuana and cocaine are mostly the same. For every drug class, extensiveness of use of the drug is very highly related to dependence on that drug. There are also effects of extensive use across drug classes. Extensiveness of marijuana use increases the risk of dependence on alcohol and cigarettes; extensiveness of alcohol use increases the risk of cigarette and marijuana dependence. By contrast, dependence on cocaine appears not to be influenced by extensiveness of use of any other substances. Sensation-seeking is a strong correlate of dependence on all drugs, except cocaine, while community social capital decreases the odds of dependence on all four drug classes.

Comorbidity of Multiple Substance Dependence and Psychiatric Syndromes Comorbidity of dependence on single and multiple drugs (cigarettes, alcohol and illicit drugs) with psychiatric comorbidity was examined in nationally representative samples of adults 18 years and older. Drug dependent individuals are at increased risk for psychiatric syndromes. Individuals uniquely dependent on one drug class, whether alcohol, cigarettes or illicit drugs, have the same risk of being comorbid on a depressive or anxiety syndrome. However, those dependent both on illicit and legal drugs are almost twice as likely to have other psychiatric disorders as those dependent on illicit drugs alone. This reflects the additive association of dependence on legal and illegal drugs with psychiatric disorders and the increased rates of dependence on a legal drug among those dependent on an illicit drug. Individuals with multiple dependencies on legal and illegal drugs have the highest need of mental health services.