Study 1
Pentz and colleagues (1989) conducted a randomized controlled trial of the Midwestern Prevention Project (MPP) in Kansas City, Missouri, a longitudinal study that spanned 6 years. The experiment began in fall 1984, and the study concentrated on providing an evaluation of the program’s impact on cigarette use prevalence among middle school students. Schools were assigned to either a program group—which received school, booster, parent, and mass media program components—or a control group that received regular health education programming in school as usual. As there was no realistic way to prevent access to the mass media component, the control group was assumed to have access to this component of the intervention. The sample included eight schools, totaling 1,122 sixth and seventh grade students. The sample was 50 percent male and 82 percent white, 14 percent African American, and 4 percent other races. To evaluate the effectiveness of MPP, the program’s impact on smoking prevalence rates was analyzed. Smoking prevalence rates were measured through an analysis of self-reported cigarette use, supplemented with a biochemical analysis of monoxide in students’ breath. Both measures were combined to determine an overall impact on smoking prevalence rates.
Self-reported cigarette use among students was measured through the administration of a questionnaire regarding smoking behavior. Students completed a self-administered questionnaire about 1½ months before the intervention, between early November 1984 and early January 1985, to provide baseline data. Three follow-ups were conducted to monitor the progress of the intervention’s effects; these occurred at 6 months, after 1 year, and after 2 years. The questionnaire included items regarding smoking behaviors, drug use, and psychological factors related to drug use, and four categories of questions were used as indicators of program effects: lifetime use, past-month use, past-week use, and current use of cigarettes.
A biochemical measure of smoking was used to enhance the accuracy of the data collected from the survey results, which entailed the collection and analysis of carbon monoxide in students’ breath. During this procedure, each student was instructed to inhale deeply and hold his or her breath for 10 seconds. Students then exhaled through a straw to blow up the balloon, after which indicator readings were recorded. The instrument was calibrated before its use, to account for levels of carbon monoxide in the air that could be from heating systems or other sources. These recordings were used to estimate the concentration of carbon monoxide in expired air from the lungs, to estimate whether cigarette use was evident. The authors conducted subgroup analyses on race and grade aggregated at the school level.
Study 2
Chou and colleagues (1998) conducted a randomized controlled trial of MPP in Indianapolis, Indiana, beginning in fall 1987. The evaluation concentrated on the impact MPP made in reducing tobacco, alcohol, and marijuana use among middle school students. A cohort of adolescents from 57 schools in 12 school districts was identified for inclusion in the study, and schools were randomly assigned to either a treatment condition or control condition. Thirty-two schools were placed in the treatment condition and used all components of the MPP curriculum. Twenty-five schools were placed in the control group and were assigned to a health-education-as-usual condition. To be eligible for participation in the study, adolescents must have reported use of cigarettes, alcohol, or marijuana in the month before baseline data collection. The number of students included in the study totaled 3,412, with 1,904 in the treatment group and 1,508 in the control group. Students were tracked for four follow-ups at 6 months, 1½ years, 2½ years, and 3½ years after baseline data collection.
The study used the administration of a self-report questionnaire regarding students’ recent substance use. The questionnaire consisted of 100 items that measured substance abuse behavior as well as demographic characteristics, attitudes, and social influences related to substance abuse. Responses regarding cigarette, alcohol, and marijuana use were evaluated separately to determine the potential impact of MPP on each behavior. The authors did not conduct subgroup analyses.