Several approaches have been proposed to model binary outcomes that arise from longitudinal studies. Most of the approaches can be grouped into two classes: the population-averaged and subject-specific approaches. The generalized estimating equations (GEE) method is commonly used to estimate population-averaged effects, while random-effects logistic models can be used to estimate subject-specific effects. However, it is not clear to many epidemiologists how these two methods relate to one another or how these methods relate to more traditional stratified analysis and standard logistic models. The authors address these issues in the context of a longitudinal smoking prevention trial, the Midwestern Prevention Project. In particular, the authors compare results from stratified analysis, standard logistic models, conditional logistic models, the GEE models, and random-effects models by analyzing a binary outcome from two and seven repeated measurements, respectively. In the comparison, the authors focus on the interpretation of both time-varying and time-invariant covariates under different models. Implications of these methods for epidemiologic research are discussed.

peer smoking on adolescents' own smoking is still a matter of debate. In addition, little research has examined the role of sign8cant others' behavior on different stages of smoking onset. In particular, not much information is available regarding gender and ethnic differences in social influences on smoking behavior. We use structural equation modeling to address these issues. Different theoretical perspectives from cognitive-affective theories (Ajzen 1985; Ajzen and Fishbein 1980) and social learning theories (Akers et al. 1979; Bandura 1969, 1982, 1986) have been integrated into a structural model of smoking influence. The results show that friends' smoking affects adolescent initiation into smoking both directly and indirectly, whereas parental smoking influences smoking initiation only indirectly. The data also show that friends' and parents' smoking affect smoking escalation only indirectly. In general, friends' smoking has a stronger effect on adolescents' smoking behavior, particularly on initiation. Multiple group comparisons of the structural models predicting smoking initiation among males and females reveal that parental approval of smoking plays a sign8cant mediating role for females, but not for males. Comparisons of Whites, Blacks, Hispanics, and other ethnic groups reveal that there are some signiJicant differences in the pathways of friends' influences among the four groups.

This article reviews major risk factors for cigarette smoking, alcohol, and other drug abuse and promising community-based approaches to primary prevention. In a longitudinal experimental study, 8 representative Kansas City communities were assigned randomly to program (school, parent, mass media, and community organization) and control (mass media and community organization only) conditions. Programs were delivered at either 6th or 7th grade, and panels were followed through Grade 9 or 10. The primary findings were (a) significant reductions at 3 years in tobacco and marijuana use and (b) equivalent reductions for youth at different levels of risk. This study provides evidence that a comprehensive community program-based approach can prevent the onset of substance abuse and that the benefits are experienced equally by youth at high and low risk.

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Evaluations of 40 mass media programs/campaigns designed to influence cigarette smoking were reviewed. Information/motivation programs/campaigns generally produced changes in awareness, knowledge, and attitudes. Extensive national campaigns also produced meaningful behavioral change. Programs/ campaigns designed to promote some specific smoking-related action produced mixed results, depending in large part on the type of promotion involved. Mass media cessation clinics were found to be effective, with media plus social support being more effective than IntroductionNinety per cent of current smokers wish to quit, but over two-thirds of them do not wish to attend a clinic to do so.2 Over the past 20 years, approximately 35 million adults have already quit smoking, and the overwhelming majority ofthem did so without the help of any organized clinic.5 It is conceivable that the mass media played some role in increasing awareness of the dangers of smoking,6 motivating so many smokers to want to quit, and helping so many exsmokers to successfully quit. This paper provides a comprehensive review of evaluated mass media programs and campaigns designed to reduce smoking behavior.Over the past 30 years, mass media programs and campaigns have been used in three major ways to influence smoking related knowledge, attitudes, and behavior: to inform the public of the negative health consequences of cigarette smoking and to try to motivate existing smokers to quit; to promote specific smoking cessation actions to those smokers motivated to quit, such as calling a hotline or requesting specific materials such a tip-sheet or a self-help manual; and to provide smoking cessation "self-help clinics" to those smokers who desire to quit. These three ways of using mass media for smoking control reflect an historical development in the use of media, that has followed Cartwright's7 suggested stages of change (awareness, motivation, and then individual behavior change). A parallel historical development has occurred in the progression from discrete media programs to the incorporation of greater community involvement.To date, at least 40 evaluated antismoking programs or campaigns have been conducted.* Nine of these were information/motivation programs/campaigns, 11 were promotions of specific cessation activities, and 20 were mass media cessation "self-help clinics". Characteristics of all

The present article describes an evaluation of a self-report questionnaire administered to whole classrooms of 7th graders. Using the test-retest reliability matrix (based on concepts of Cronbach [ 11 and Campbell and Fiske [ 2]), eight of nine drug-use indices appeared to have acceptable to good reliability. The three measures included in the test-retest reliability matrix provide stronger evidence for good reliability than could any single measure.

Most school-based smoking prevention studies employ designs in which schools or classrooms are assigned to different treatment conditions while observations are made on individual students. This design requires that the treatment effect be assessed against the between-school variance. However, the between-school variance is usually larger than the variance that would be obtained if students were individually randomized to different conditions. Consequently, the power of the test for a treatment effect is reduced, and it becomes difficult to detect important treatment effects. To assess the potential loss of power or to calculate appropriate sample sizes, investigators need good estimates of the intraclass correlations for the variables of interest. The authors calculated intraclass correlations for some common outcome variables in a school-based smoking prevention study, using a three-level model-i.e., students nested within classrooms and classrooms nested within schools. The authors present the intraclass correlation estimates for the entire data set, as well as separately by sex and ethnicity. They also illustrate the use of these estimates in the planning of future studies.

This study examined the effects of smoking policy on 4,807 adolescents in 23 schools over a two-county area in California. Amounts