Mediation in a Family-Directed Program for Prevention of Adolescent Tobacco and Alcohol Use

Preventive Medicine 33, 333–346 (2001) doi:10.1006/pmed.2001.0892, available online at http://www.idealibrary.com on

Mediation in a Family-Directed Program for Prevention of Adolescent Tobacco and Alcohol Use Susan T. Ennett, Ph.D.,*,1 Karl E. Bauman, Ph.D.,* Michael Pemberton, Ph.D.,† Vangie A. Foshee, Ph.D.,* Ying-Chih Chuang, M.P.H.,* Tonya S. King, Ph.D.,‡ and Gary G. Koch, Ph.D.§ *Department of Health Behavior and Health Education and §Department of Biostatistics, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599; †Health and Social Policy Division, Research Triangle Institute, Research Triangle Park, North Carolina; and ‡Department of Health Evaluation Sciences, Pennsylvania State University College of Medicine, University Park, Pennsylvania Published online August 23, 2001

Background. Family Matters is a universal intervention designed to prevent adolescent tobacco and alcohol use through involvement of family members and by targeting family risk factors for tobacco and alcohol use. Previously reported findings suggest that the program reduced the prevalence of both adolescent smoking and drinking in the 12 months after program completion. This paper reports analyses conducted to identify the mediators through which the program influenced adolescent smoking and drinking. Methods. One thousand fourteen adolescents ages 12 to 14 years and their families, identified by randomdigit dialing, were entered into a randomized trial. Adolescents and their parents provided data by telephone for measuring mediator and behavioral variables at baseline, 3 months, and 12 months after program completion. Repeated-measures logistic regression with generalized estimating equations was used to assess mediation processes. Results. The program resulted in statistically significant changes in several substance-specific aspects of the family, such as rule setting about tobacco and alcohol use. However, the intermediate family effects did not account for the program effects on adolescent behavior. Conclusions. The variables hypothesized to explain program effects were not identified by direct empirical examination. 䉷 2001 American Health Foundation and Academic Press

This research was supported by Grant R01 DA08125 from the National Institute on Drug Abuse, National Institutes of Health, U.S. Department of Health and Human Services. 1 To whom reprint requests should be addressed at the Department of Health Behavior and Health Education, University of North Carolina at Chapel Hill, CB 7440, Rosenau Hall, Chapel Hill, NC 27599. Fax: (919) 933-2921. E-mail: [email protected].

Key Words: adolescence; tobacco; alcohol; family; drug use prevention.

INTRODUCTION

Family-based interventions for prevention of adolescent drug use are recognized as a promising avenue for intervention, but few family interventions targeting the general population have been developed and fewer still rigorously evaluated [1–3]. Most family-based interventions evaluated in controlled trials are clinical interventions and involve high-risk children and families [4]. Family Matters is a universal, family-directed intervention to prevent adolescent tobacco and alcohol use. As a universal intervention, it is intended for all families with early adolescents rather than for subgroups of high-risk families [5, 6]. Family Matters targets the family as a source of both positive and negative influences on adolescent tobacco and alcohol use and focuses on changing these characteristics. The targeted characteristics derive from the substantial research that suggests that families influence the development of adolescent drug use both through global attributes of the family, such as supervision and attachment [7–11], and through drug-specific characteristics, such as parental drug use and tolerance of drug use [12–14]. When the family is included in intervention, these family risk factors can be directly targeted for change. The present investigation extends our prior work. As elaborated below, we evaluated Family Matters with a randomized trial involving a general population sample of adolescents and their families [15]. Findings suggested that the program significantly reduced the prevalence of both adolescent smoking and drinking in the 12 months after program completion [16]. In this paper,

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0091-7435/01 $35.00 Copyright 䉷 2001 by American Health Foundation and Academic Press All rights of reproduction in any form reserved.

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we report analyses designed to identify the mediators that account for the influence of the program on adolescent smoking and drinking. In the field of adolescent substance use prevention, only a few studies have examined the extent to which program effects on hypothesized mediator variables account for reductions in drug use attributable to the program [17–19]. More typically, when hypothesized mediator variables have been assessed, they have been examined as program outcomes without doing the direct analyses necessary to determine whether they are responsible for drug use effects [3, 20–22]. Evidence of mediation requires statistically significant program effects on both hypothesized mediator variables and program outcomes, statistically significant associations between the hypothesized mediator variables and program outcomes, and reduction in the program-to-outcome relationship when the mediator variables are controlled [23–25]. Assessment of mediation processes is key to program development by elucidating whether programs achieve effects in the ways they are intended [24]. Family Matters consists of successive mailings of four booklets to parents of 12- to 14-year-old adolescents and telephone discussions between parents and health educators after each mailing. The content of the booklets was guided by our conceptual model, described below, which we derived from theory and prior research concerning family factors in adolescent tobacco and alcohol use. The booklets provide background information in a question-and-answer format for parents to read and describe several simple activities to be conducted within the family that reinforce the program content. Across the four booklets, there are 15 activities. Some are for the parents only, but most are designed for the adolescent and family members. The full set of program materials is available at our Web site (http:// www.sph.unc.edu/familymatters) and the program is described in more detail elsewhere [26]. The conceptual model underlying Family Matters is shown in Fig. 1. The intervention was designed to bring about change in two broad domains of family life: global family characteristics and substance-specific family characteristics. Change in these domains was expected to influence a third domain, adolescent cognitions about

FIG. 1. Family Matters program effects conceptual model.

tobacco and alcohol use, and, in turn, to influence adolescents’ tobacco and alcohol use. As well as showing pathways for indirect program effects on adolescent cognitions through change in the family environment, the model shows the potential for direct program effects on adolescent cognitions. Because the program is delivered to the adolescent only through the family, however, we give more credence to the possibility that adolescents are indirectly influenced through family change. Regardless, the conceptual model suggests that behavioral effects will be brought about through intervening at two levels: the family level and the adolescent level. Each of the three domains of mediators includes several specific mediators, which are linked to one or more program components. Global family characteristics include parenting practices and features of the parent– child relationship that promote healthy development and hence avoidance of tobacco and alcohol use. Following research evidence, the program stresses the importance of showing affection and respect within the family, of talking and listening to each other, and of spending time together, as well as the need for parents to set clear and firm expectations for behavior [8, 9, 27–30]. These characteristics are central to theories of socialization [31–33], social control [34], and family interaction [9]. An example activity is “Family Time,” which suggests how families can plan and then set aside time for fun activities to be done together, with each family member having the chance to choose an activity. The activity has no drug-related focus; its purpose is to encourage enjoyable interactions among the family and adolescent and hence promote positive family relationships. Substance-specific family characteristics include practices that may convey tolerance for adolescent tobacco and alcohol use, such as the example parents set with their own tobacco and alcohol use, the attitudes they express to their children about smoking and drinking, their attentiveness to the availability of tobacco and alcohol in the home, their setting and following through on family rules about smoking and drinking, their monitoring for clues of adolescent use, and their efforts to help adolescents deal with pressures to use tobacco and alcohol arising from peers and the media. Identification of these family characteristics as risk factors also is based on prior research [9, 12, 14, 35], with most of the substance-specific variables being encompassed by social learning theory [35, 36]. Family Matters includes content relevant to each area through information provided in the booklet question-and-answer sections and activities. An example activity, “The Rules of the House,” encourages families to make and discuss family rules about smoking and drinking. The activity provides example rules, while indicating that not all rules work for every family and that each family must choose the rules that best fit them. In this activity and

ADOLESCENT TOBACCO AND ALCOHOL USE MEDIATORS

a subsequent activity, guidance is given for creating fair rules, talking about rules, agreeing on rewards and consequences for following or not following the rules, and monitoring and reinforcing the rules. Adolescent cognitions about tobacco and alcohol use include adolescents’ expectations about the consequences of use and their intentions to smoke and drink, both of which represent prominent and proximal risk factors for drug use [37, 38] and are featured in expectancy-value theories of adolescent drug use [35, 39]. The entire program is intended to influence adolescents’ intentions not to use tobacco and alcohol, with some activities more specifically focused on reinforcing adolescent beliefs about drug nonuse. An example activity is “Story Time,” which presents two stories that involve an adolescent in a dilemma about tobacco or alcohol use. The stories, to be read out loud by the family, are followed by several questions that encourage family conversation about consequences of tobacco and alcohol use and ways of avoiding difficult situations. In this way, the activity reinforces a global family characteristic—communication—and promotes substance-specific conversation between the adolescent and the family to help the adolescent recognize both negative and positive consequences of use and nonuse and to underscore to the adolescent his or her own susceptibility to those consequences. In sum, Family Matters includes content to make parents aware of the continued importance of their guiding role as the child enters adolescence and provides activities to enhance the overall quality of family life and to promote family considerations of tobacco and alcohol use that reinforce nonuse. The program content is reinforced by the health educators who talk with parents after completion of each booklet. Through bringing about change in parents and through structuring interactions between the adolescent and the family members, the intention is to help parents use effective parenting practices and assist them in giving clear and specific guidance to teens on their expectations concerning tobacco and alcohol use. These family interactions are meant to promote prevention of onset among adolescent nonusers and reduction or cessation of use among adolescents who have already tried smoking and drinking. We implemented Family Matters between July 1996 and September 1997. Families who completed the entire program (74.1% of the 549 families who began the program) spent an average total of almost 4 1/2 h doing the program and parents spent an additional hour talking with the health educator by telephone. The majority of families completed all activities associated with each booklet [26]. The program took an average of about 6 months to complete. As reported previously, Family

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Matters had significant effects on the overall prevalence of adolescent smoking and drinking [16]. Examination of mediators of these program effects on overall prevalence of use—as opposed, for example, to effects on onset of use only—is appropriate because the program is intended for families of adolescent nonusers and users and because there is evidence that the program impacted prevalence. METHODS

Research Design To evaluate the Family Matters program, a probability sample of adolescents ages 12 to 14 years and their families throughout the contiguous states of the United States was entered into a randomized trial. Participants enrolled in the study were identified through random-digit dialing. As eligible families were screened, they were offered the opportunity to participate in the study and told that they had a 50/50 chance of receiving the Family Matters program. The 1,316 adolescent–parent pairs who agreed to be enrolled in the study are 55.4% of households estimated to be eligible for the study. The pairs completed baseline interviews by telephone, were matched with another pair by date and time of completion, and then were randomly assigned either to receive Family Matters or to serve as controls. Within a month after the baseline interview, the treatment families began the program. Three months and 12 months after the treatment family completed the program, follow-up telephone interviews were conducted with both the adolescent and the parent in the treatment and control pairs. Of the 1,316 adolescent–parent pairs in the study, 1,014 (77.1%) completed both the follow-up 1 and the follow-up 2 interviews. These adolescent–parent pairs form the sample for these analyses. Data Collection Parents provided verbal consent for their own and their children’s participation in the study and adolescents provided verbal consent for their participation. All procedures were reviewed and approved by our institutional review board. The mother or mother surrogate was the parent interviewed in 96.3% of the cases. The parent and adolescent baseline and follow-up 1 and 2 interviews lasted approximately 15 min and were conducted by female interviewers. Interviewers were blind to the study condition of respondents and were not the same staff as the health educators who talked with treatment parents over the course of the intervention. To help assure privacy for the adolescents, the interviewer verified the privacy of the adolescent before beginning the interview and rescheduled the phone call if necessary. The interviewer read possible responses

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to questions about adolescent smoking and drinking, with instructions for the adolescent to respond with “stop” after hearing the appropriate response. Hence, the adolescent never could be heard admitting tobacco or alcohol use in the home. Sample Approximately half of adolescent respondents were female (50.7%), the average age was 13.9 years (SD ⫽ 0.9), and the race/ethnicity composition was 78% nonHispanic white, 9.9% non-Hispanic black, 7.6% Hispanic, and 4.5% of other race/ethnicity. Most adolescents lived in two-parent households (82.4%). Slightly more than one-third of the respondents’ mothers had a high school education or less (36.2%), about one-third had some college education (33.2%), and about onethird had graduated from college or more (32.0%). Except for mother education, respondents were generally similar in sociodemographic characteristics to families with children 12 to 14 years of age in the 1990 U.S. Census [40, 41]. Parent respondents had more formal education than the general population, as is often the case when telephone numbers are sampled [42]. Randomization provided similar treatment and control groups on all sociodemographic characteristics except race/ethnicity: There were fewer non-Hispanic whites in the treatment (73.6%) than control group (81.8%) (␹ 2 ⫽ 10.06, P ⫽ 0.002). To assess attrition bias after baseline, we compared sample characteristics for respondents who completed both follow-up interviews (i.e., the analysis sample) and for respondents who did not complete both follow-up interviews. Respondents lost to follow-up were more likely to have smoked cigarettes (33.1% vs 26.8%, ␹ 2 ⫽ 4.65, P ⫽ 0.031), be of other race/ethnicity than nonHispanic white (42.1% vs 22.0%, ␹ 2 ⫽ 47.97, P ⬍ 0.001), live in single-parent homes (33.4% vs 17.6%, ␹ ⫽ 34.86, P ⬍ 0.001), and have mothers with high school education or less (54.8% vs 36.2%, ␹ 2 ⫽ 46.11, P ⬍ 0.001). Analysis of differential attrition across treatment groups revealed no differences, however, except for race/ ethnicity: Whites in the treatment group (74.7%) were less likely than whites in the control group (88.5%) to complete follow-up interviews, whereas about the same percentage of other race/ethnicity respondents in the treatment (64.6%) and control groups (62.7%) completed follow-up interviews (Wald ␹ 2 ⫽ 13.44, P ⬍ 0.001). The sociodemographic variables are controlled for in all analyses. Measures The measures include exposure to the Family Matters program, adolescent tobacco and alcohol use, three sets of mediator variables, and sociodemographic characteristics. The sets of mediator variables correspond

to the conceptual model shown in Fig. 1 and are global family characteristics, substance-specific family characteristics, and adolescent cognitions. All the mediator variables are coded so that lower scores are in the hypothesized direction of a beneficial program effect. Internal consistency reliability, as assessed by Cronbach’s ␣, is reported for multiple-item measures; the average intercorrelation among items is also reported for measures comprising 2 or 3 items. The correlations among the global and substance-specific family characteristic measures are shown in Table 1. None of the correlations is above 0.56 and most are less than 0.15, suggesting that the measures are not redundant. Adolescent tobacco and alcohol measures were based on self-reports and include smoking and drinking at baseline, follow-up 1, and follow-up 2. At each data collection wave, adolescents were asked how much they had ever smoked and how much alcohol they had ever had in their lifetime. They were told not to consider alcohol they may have had as part of a religious service. Adolescents who reported no smoking, not even a puff, were coded as nonusers and adolescents who had at least puffed on a cigarette were coded as users. Similarly, adolescents who reported no drinking, not even a sip, were coded as nonusers and adolescents who had at least sipped alcohol were coded as users. Mediators measuring global family characteristics were measured by parent reports and include parental supervision, supportiveness, involvement, and communication. Parental supervision was formed from the sum of responses to 9 items that measured whether the adolescent had curfews on weekend and school nights and the parent’s knowledge about the adolescent’s friends, whereabouts after school, and use of free time (range 0–21; ␣ ⫽ 0.56). Supportiveness was measured by the sum of 3 items that described such aspects of the parent–child relationship as helping the adolescent when needed and providing encouragement (range 0–9; ␣ ⫽ 0.36; average intercorrelation 0.18). Involvement was measured by the sum of 2 items that measured time the parent and adolescent spent together talking and having fun (range 0–6; ␣ ⫽ 0.69; average intercorrelation 0.53). Communication was measured by a single item that asked parents the extent to which they gave an explanation when requesting the adolescent to do something (range 0–3). Mediators measuring substance-specific family characteristics were based on parent responses and include separate measures for tobacco and alcohol. The measures are parent’s expectations for negative consequences of adolescent smoking and drinking, parent’s attitude toward adolescent use, parent’s encouragement not to use, parental use, rules about use, monitoring of use, availability of cigarettes and alcohol in the home, and discussion about nonfamily influences on use. Parent’s expectation for negative consequences of

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TABLE 1 Correlations between Measures of Family Characteristics: Correlations for the Tobacco Sample Are above the Diagonal and for Alcohol Sample Are below the Diagonal

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Supervision Support Communication Involvement Expected consequences Parental attitude Parental encouragement Parental use Rules about use Monitoring Availability Nonfamily influences

1

2

3

4

5

6

7

8

9

10

11

12

1.0 0.24 0.12 0.32 0.12 0.05 0.04 0.11 0.03 ⫺0.02 0.02 0.09

0.26 1.0 0.20 0.34 0.09 0.03 0.09 0.05 0.10 0.03 0.07 0.12

0.11 0.17 1.0 0.26 0.08 0.07 0.02 0.08 0.04 0.03 0.02 0.10

0.31 0.34 0.25 1.0 0.02 0.01 0.09 0.05 0.08 0.01 0.03 0.20

0.09 0.04 0.10 0.08 1.0 0.32 0.09 0.09 0.08 0.05 0.02 0.08

0.06 0.04 0.08 0.07 0.16 1.0 0.05 0.12 0.07 0.05 0.07 0.08

⫺0.01 0.03 0.03 0.08 0.00 ⫺0.01 1.0 0.03 0.56 0.14 0.24 0.53

0.12 0.06 0.09 0.14 0.11 0.13 ⫺0.01 1.0 0.11 ⫺0.00 0.15 0.14

0.01 0.12 0.04 0.13 ⫺0.00 0.01 0.56 ⫺0.13 1.0 0.30 0.31 0.50

⫺0.01 ⫺0.00 0.01 ⫺0.04 ⫺0.01 0.01 0.12 ⫺0.15 0.25 1.0 0.18 0.21

⫺0.01 0.06 0.04 0.02 0.04 ⫺0.01 0.21 ⫺0.00 0.29 0.31 1.0 0.26

0.11 0.15 0.09 0.15 0.09 0.04 0.47 0.03 0.53 0.21 0.27 1.0

Note. Pearson correlation coefficients are shown. Sample sizes for the correlations between tobacco measures range from 776 to 791; sample sizes for the correlations between alcohol measures range from 980 to 1014. All correlations ⱖ 0.07 are statistically significant at P ⬍ 0.05 or better.

use was based on a single item measuring whether “only good things would happen, both good and bad things would happen, or only bad things would happen” if the adolescent smoked cigarettes (drank alcohol). Parent’s attitude toward use was measured by a question asking how much “would you like it or dislike it if (adolescent) smoked cigarettes (drank alcohol) now.” Because of the tendency of parents to endorse only the most negative responses, for both the expected consequences and the attitude measures, we created binary variables in which the most negative response (i.e., “only bad things would happen” and “dislike it a lot”) was contrasted with all other responses. Parental smoking (drinking) was coded as 0, 1, or 2 parents currently smoke (drink). Measures of rules about tobacco (alcohol) use were formed from responses to 3 items measuring the frequency with which parents talked with the adolescent about rules and discipline concerning use and actually told the adolescent that use was not allowed (range 0–9; smoking rules ␣ ⫽ 0.76; smoking rules average intercorrelation 0.62; alcohol rules ␣ ⫽ 0.83; alcohol rules average intercorrelation 0.52). Monitoring of use was measured by a single item about the frequency of parent’s checking the adolescent’s room or clothes for evidence of tobacco (alcohol) use. Availability of tobacco (alcohol) in the home was measured by a single item that asked how many times the parent had made it more difficult for the adolescent to get tobacco (alcohol) at home. The measure of discussion about nonfamily influences on adolescent tobacco (alcohol) use was formed from summing 3 items about the frequency of discussion about peer and media influences (range 0–9; influences on smoking ␣ ⫽ 0.74; influences on smoking average intercorrelation 0.49; influences on drinking ␣ ⫽ 0.70; influences on drinking average intercorrelation 0.45). All of the individual items making up the

measures of rules, monitoring, availability, and nonfamily influences had four response options ranging from 0 to 3 or more times. Mediators measuring adolescent cognitions include adolescents’ expectations about the negative consequences of smoking and drinking and their future intentions to smoke and drink. The expected consequences measures were formed from questions similar to those asked the parent. Adolescents who responded that “only bad things would happen” as a result of smoking (drinking) were contrasted with adolescents who gave any other response. To measure behavioral intentions, adolescents were asked the likelihood of smoking one or more cigarettes (drinking one or more drinks) between now and age 18. Response options ranged from “won’t for sure” to “for sure” on a 5-point scale. The sociodemographic measures included adolescent age (12, 13, or 14 years), sex, race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, other race/ ethnicity), family structure, and mother’s education. For most analyses, the race/ethnicity categories were collapsed to contrast non-Hispanic white youth with all other race/ethnicity category youth because there were too few respondents in each minority race/ethnicity category for separate analyses. Family structure was coded as whether the adolescent lived with two parents in the household or lived in other than a two-parent household. Mother’s education was measured with three categories: high school graduate or less, technical/ vocation school or some college, or college graduate or higher. Data Analysis Our mediation analysis follows the approach outlined by Baron and Kenny [23] to assess whether the extent

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to which change in behavioral outcomes as a result of the Family Matters program is accounted for by change in the proposed mediators. We conduct the analysis in four parts to assess each condition necessary to demonstrate mediation. We first establish that the program produced differences between treatment and control respondents in smoking and drinking behavior. Our sample consists of respondents who completed both of the follow-up interviews. This sample allows us to ensure the appropriate temporal ordering of the mediator and behavior variables by measuring change in the mediator variables from baseline to follow-up 1 and change in the behavioral variables from baseline through follow-up 2. Our previously reported findings on program effects included respondents who completed either one or both follow-up interviews, yielding a slightly larger sample than for the present analyses and the need to verify that behavioral effects were also present in the current sample. We use repeated measures logistic regression with generalized estimating equation (GEE) methods for analysis of program effects on adolescent behavior [43, 44]. GEE methods provide for appropriate treatment of correlated data due to the repeated-measures design (i.e., adolescent smoking and drinking were assessed for each respondent three times). We estimate the effect of the program on prevalence of adolescent smoking and drinking for the 12 months after program completion, after controlling for baseline use and the sociodemographic variables. We also examine program interactions with race/ethnicity and the other sociodemographic variables in predicting both smoking and drinking prevalence. Note that because our measures of tobacco and alcohol use are based on dichotomous reports of ever use, by definition, baseline users cannot decrease use at follow-up. Thus, any program effects observed must be attributable to prevention of onset. We do not use measures of frequency or quantity of use, however, because of the skewness of the measures. The vast majority of adolescents at this age who use tobacco and alcohol do not use them frequently or in high quantity. To satisfy the second condition that must be met to demonstrate mediation—program effects on the mediator variables—we examine whether the program was associated with change from baseline to follow-up 1 in the mediator variables. We use logistic and linear regression, depending on whether the change score for the mediator variable was measured categorically or continuously, respectively. The analyses control for the baseline value of the mediator and sociodemographic variables. Consistent with our conceptual model, potential mediators include global and substance-specific family characteristics significantly impacted by the program and adolescent cognitions either directly affected by the program or significantly associated with a family variable that was influenced by the program. To assess

the latter possibility, we assess whether change in each family variable was associated with change in each adolescent cognition variable. Third, using logistic regression models with GEE methods, we identify the mediator variables significantly associated with adolescent smoking and drinking by examining the relationship between change in the mediator from baseline to follow-up 1 and change in adolescent smoking or drinking from baseline through follow-up 2, after controlling for the sociodemographic variables. Finally, to directly assess the presence of mediation, again using logistic regression models with GEE methods, we examine change in the magnitude and statistical significance of the program effects over the 12-month follow-up period, now with both the baseline value and the change in the potential mediators from baseline to follow-up 1 in the model, as well as baseline behavior and sociodemographic variables. Mediation is indicated by a decrease in the magnitude and significance of the program effect. The potential mediators in the final model include only those variables that meet conditions 2 and 3. Because beneficial program effects on mediators and behavior are hypothesized (i.e., strengthening of mediators believed to be protective against substance use, decrease in mediators that are risks for substance use, and reductions in adolescent smoking and drinking), we use the one-tailed test (␣ ⫽ 0.05) for all analyses and provide lower bound 95% confidence limits for program effects on adolescent smoking and drinking. Hence, in identifying mediator variables that meet conditions 2 and 3, as described above, we include only those that were significantly influenced by the program in the hypothesized direction and that significantly influenced behavior in the hypothesized direction. Our intent is to explain the beneficial program effects on adolescent smoking and drinking. RESULTS

Program Effects on Prevalence of Adolescent Smoking and Drinking The program had statistically significant effects on the prevalence of adolescent smoking and drinking. The effect on adolescent smoking was moderated by race/ ethnicity, such that the program effect was present for non-Hispanic white youth only. For the subset of nonHispanic white adolescents (N ⫽ 791), adolescents in the control group were more than one and one-half times as likely to smoke at follow-up as adolescents in the treatment group (OR ⫽ 1.59, P ⫽ 0.008, lower bound confidence limit 1.19). No other sociodemographic variable significantly moderated program effects on smoking. Treatment–control comparison of drinking prevalence showed that the odds of drinking were almost one and one-half times greater for adolescents in the control

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group than for adolescents in the treatment group (OR ⫽ 1.38, P ⫽ 0.02, lower bound confidence limit 1.07) and there were no interactions involving the sociodemographic variables. We proceed with analysis of mediators of these program effects using the non-Hispanic white subsample for analyses related to smoking and using the full sample for analyses when considering drinking.

media influence smoking and drinking. Significant improvement in parent–child involvement as a result of the program was found for non-Hispanic whites but not for the full sample. Adolescents exposed to the program were significantly less likely to intend to smoke.

Program Effects on Mediators

The associations between change in family characteristics and change in adolescent cognitions are shown in Table 3. Positive regression coefficients and odds ratios greater than 1.0 indicate that change in family characteristics was associated with change in adolescent cognitions in the hypothesized direction. In the non-Hispanic white sample, improved communication was associated with increased adolescent expectations of negative consequences of smoking; increased parental supervision and involvement and decreased parental smoking were associated with decreased adolescent intentions to smoke. In the full sample, greater parental supervision and more negative attitude toward drinking were associated with increased adolescent expectations of negative consequences of drinking; more negative attitude toward drinking, greater encouragement not to drink, and decreased parental drinking were associated with decreased adolescent intentions to drink. Because the program influenced none of the family variables significantly associated with adolescent cognition variables, no additional adolescent cognition variables were identified as candidates for mediation.

Table 2 presents the effects of Family Matters on global and substance-specific family characteristics and adolescent cognitions separately for the non-Hispanic white and full samples. Negative ␤’s and odds ratios less than 1.0 indicate lower scores for the treatment group, and hence a program effect in the predicted direction. For both non-Hispanic whites and the full sample, the program had fewer significant effects on global family characteristics than on either tobacco- or alcoholspecific family characteristics. As a result of the program, parents were significantly more likely to encourage their children not to smoke, to set rules about smoking and drinking, and to discuss how peers and the TABLE 2 Family Matters Effects on Global and Substance-Specific Family Characteristics and Adolescent Cognitions Regression coefficientsa,b

Outcomec Global family Supervision Support Communication Involvement Substance-specific Expected consequences Parental attitude Parental encouragement Parent use Rules about use Monitoring Availability in home Nonfamily influences on use Adolescent cognitions Expected consequences Intentions to use

Tobacco model Non-Hispanic whites (N ⫽ 791)

Alcohol model Full sample (N ⫽ 1,014)

0.03 0.05 0.03 ⫺0.10*

⫺0.00 0.08 0.00 ⫺0.03

OR ⫽ 0.80 OR ⫽ 0.57 ⫺0.42** ⫺0.02 ⫺0.46** OR ⫽ 0.95 ⫺0.07 ⫺0.76**

OR ⫽ 0.86 OR ⫽ 1.14 ⫺0.10 ⫺0.04 ⫺0.77** OR ⫽ 0.77 ⫺0.08 ⫺0.74**

OR ⫽ 1.04 ⫺0.15**

OR ⫽ 1.35 0.03

For continuous measures, the presented numbers are ␤’s; for dichotomous measures, the presented numbers are odds ratios. b Negative ␤’s or odds ratios ⬍1 indicate lower scores for the treatment group (a program effect in the predicted direction). c All responses are for the change from baseline to follow-up 1 (3 months after intervention). All responses are from parents, except for Adolescent cognitions, which are from adolescents. * P ⬍ 0.05. ** P ⬍ 0.01. a

Associations between Change in Family Characteristics and Adolescent Cognitions

Mediator Effects on Behavior Table 4 shows the effects of the family characteristic and adolescent cognition variables on adolescent smoking and drinking. Stricter parental supervision resulted in decreased adolescent smoking and drinking. In addition, decreased parental smoking was associated with reduced adolescent smoking, and decreased parental drinking was associated with reduced adolescent drinking. Greater parent–child involvement also was associated with reduced adolescent drinking. For both smoking and drinking, change for the better in both of the adolescent cognition variables was significantly associated with reduced substance use. Assessment of Mediation In the non-Hispanic white sample, only adolescent intentions to smoke met the conditions necessary to qualify as a potential mediator variable by being both significantly influenced by the program and a significant predictor of adolescent smoking. After adjusting for this mediator variable, the odds ratio for the program effect on smoking fell from 1.59 (P ⫽ 0.004, lower bound confidence limit 1.19) to 1.45 (P ⫽ 0.002, lower

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TABLE 3 Associations between Change in Family Characteristics at Follow-up 1 and Change in Adolescent Cognitions at Follow-up 1 Tobacco model Non-Hispanic whites (N ⫽ 791)

Family characteristic Global family Supervision Support Communication Involvement Substance-specific Expected consequences Parental attitude Parental encouragement Parent use Rules about use Monitoring Availability in home Nonfamily influences on use

Expect negative consequences of usea (odds ratio)

Intentions to useb ( ␤)

Alcohol model Full sample (N ⫽ 1,014) Expect negative consequences of usea (Odds ratio)

1.08 1.18 1.56** 1.14

0.05** ⫺0.09 ⫺0.05 0.10*

1.11** 1.12 1.21 1.12

1.77 2.42 0.97 1.28 0.97 0.60 0.91 0.99

0.05 0.05 ⫺0.04 0.23** ⫺0.03 ⫺0.10 ⫺0.09 ⫺0.02

1.03 1.80* 1.01 1.00 1.01 0.83 1.03 1.03

Intentions to useb (␤) 0.00 0.02 ⫺0.05 0.04 0.05 0.29* 0.04** 0.10* 0.01 0.05 0.05 0.00

a The Expect negative consequences measures are dichotomous, and the presented numbers are bivariate odds ratios obtained from logistic regression. Odds ratios ⬎1 indicate that positive changes in family characteristics were associated with positive changes in adolescent cognitions. b The Intentions measures are continuous, and the presented numbers are bivariate ␤’s obtained from regression models. Positive ␤’s indicate that positive changes in family characteristics were associated with positive changes in adolescent cognitions. * P ⬍ 0.05. ** P ⬍ 0.01.

bound confidence limit 1.07). This relatively small change suggests that the program effect on adolescent smoking was not primarily through its effect on adolescent intentions to smoke. In the full sample, none of the potential mediator variables met the necessary conditions for mediation; hence no further assessment of mediators of the program effect on adolescent drinking was conducted. Additional Analyses Because our analyses did not reveal substantial program mediators, we conducted additional analyses to investigate potential explanations. One explanation may rest in our measurement of family characteristics. For some of the measures (e.g., supportiveness), the reliability, as measured by internal consistency, was lower than desirable. Rather than omit constructs with low reliabilities from the analysis, we opted to include all constructs in the initial tests of the conceptual model. However, it could be that our a priori choice of items to measure global and substance-specific family characteristics did not represent the optimal groupings of items. As one approach to investigating this possibility, we subjected the individual items used to measure the set of global and substance-specific family characteristics to factor analysis.

Factor analysis, using principal components analysis and oblique rotation, was conducted separately for the non-Hispanic white and full samples. Analysis of the non-Hispanic white sample resulted in eight factors measuring global and tobacco-specific family characteristics. Analysis of the full sample also resulted in eight factors measuring global and alcohol-specific family characteristics. The factors identified in the nonHispanic white and full samples differed somewhat, but both included factors that tapped communication with the adolescent about use, attachment, supervision, parent attitudes toward use, and monitoring of use. Hence, the factors identified generally were similar to the measures of family characteristics specified a priori. Reliabilities (Cronbach’s ␣) for factors with 3 or more items ranged from low (0.39) to high (0.86), indicating that the factor analysis approach to measurement was not completely successful in enhancing measurement reliability. We then repeated our mediation analysis using the factor analysis-derived measures (results not shown). Analyses with the non-Hispanic white sample showed significant program effects in the expected direction on communication with the adolescent about smoking, rules about smoking, and monitoring. Analyses with the full sample showed significant program effects on

ADOLESCENT TOBACCO AND ALCOHOL USE MEDIATORS

TABLE 4 Global and Substance-Specific Family Characteristics and Adolescent Cognition Effects on Adolescent Smoking and Drinking Regression coefficientsa,b

Outcomec Global family Supervision Support Communication Involvement Substance-specific Expected consequences Parental attitude Parental encouragement Parent use Rules about use Monitoring Availability in home Nonfamily influences on use Adolescent cognitions Expected consequences Intentions to use

Tobacco model Non-Hispanic whites (N ⫽ 791)

Alcohol model Full sample (N ⫽ 1,014)

0.16** ⫺0.14 0.13 0.16

0.18** 0.01 0.10 0.21**

0.41 ⫺0.20 ⫺0.06 0.60** ⫺0.02 ⫺0.85 ⫺0.03 0.04

0.24 0.01 0.00 0.26** ⫺0.05 0.10 0.04 ⫺0.03

1.82** 0.85**

1.34** 0.20**

a The coefficients are from GEE models in which smoking and drinking behaviors were measured at both follow-up 1 (3 months after intervention) and follow-up 2 (12 months after intervention). b Positive coefficients indicate that positive change in the mediator was associated with less adolescent smoking or drinking. c The mediators are difference scores from baseline to follow-up 1 (3 months after intervention). ** P ⬍ 0.01.

communication about alcohol use. However, these factor-analysis-derived mediator variables were not significantly associated with either adolescent drinking or smoking. Hence, we did not further assess mediation as none of the potential mediators derived by factor analysis proved to be candidates by meeting all preliminary conditions for mediation. A second explanation for our failure to identify program mediators may rest in the use of parent reports to characterize the family environment. Perhaps adolescent perceptions of the family environment are more informative for understanding how adolescents experience effects of the program that might influence their smoking and drinking behavior. To examine this possibility, we created parallel measures of the global and substance-specific family characteristics based on adolescent reports. With the exception of questions about parents’ expectations for the consequences of adolescent smoking and drinking and parental monitoring of adolescent behavior, adolescents responded to questions about global and substance-specific family characteristics that were similar to those asked of parents. Hence,

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using adolescent reports, measures of parental supervision, support, communication, and involvement were formed. In addition, measures were created of adolescent perceptions of parental attitudes toward smoking and drinking, parental encouragement not to smoke or drink, parental use, rules about use, availability of tobacco and alcohol in the home, and discussion of nonfamily influences on smoking and drinking. The ␣ coefficients for the multi-item adolescent report measures tended to be higher (range 0.66–0.87) than for the measures based on parent reports. Note that an alternative approach to creating measures based on adolescent reports would be to create multiagent measures based on both parent and adolescent reports of the same construct. However, consistent with our expectation that adolescents may perceive the family environment differently compared with their parents, examination of the correlation matrix of parent and adolescent measures showed that most correlations were small (range ⫺0.01 to ⫺0.26). The exceptions were for the correlations between adolescent and parent reports of parents’ smoking (r ⫽ 0.91) and drinking (r ⫽ 0.61). The otherwise small correlations suggested the inappropriateness of combining adolescent and parent reports. Hence, we proceeded with our mediation analyses using only the adolescent-report measures. Examination of program effects on the mediators showed that for the non-Hispanic white sample, significant program effects were detected on adolescent perceptions of parental support and rules about smoking (Table 5). As reported earlier, the program resulted in decreased adolescent intentions to smoke. With respect to drinking, for the full sample, significant program effects in the hypothesized direction were present for parental support, parental rules about drinking, and discussion of nonfamily influences on alcohol use. Overall, the results are similar to those obtained when parent reports are the data source for family characteristics. When adolescent reports are used to measure family characteristics, there are many statistically significant associations between change in family characteristics and change in adolescent cognitions. As shown in Table 6, positive changes in all the global family characteristics and most of the substance-specific family characteristics as perceived by the adolescent were significantly associated with decreased intentions to smoke and drink. In addition, for more than half of the family variables, positive change was significantly associated with increased adolescent expectations for negative consequences of either smoking or drinking. These results identify adolescent expected consequences of smoking and intentions to drink as potential mediator variables because both were significantly associated with a family variable directly influenced by the program.

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TABLE 5 Family Matters Effects on Global and Substance-Specific Family Characteristics and Adolescent Cognitions, Adolescent Reports Regression coefficientsa,b

Outcomec Global family Supervision Support Communication Involvement Substance-specific Expected consequences Parental attitude Parental encouragement Parent use Rules about use Monitoring Availability in home Nonfamily influences on use Adolescent cognitions Expected consequences Intentions to use

Tobacco model Non-Hispanic whites (N ⫽ 791) 0.00 ⫺0.16** ⫺0.09 0.04

Alcohol model Full sample (N ⫽ 1,014) ⫺0.02 ⫺0.12* ⫺0.05 0.04

— OR ⫽ 1.30 ⫺0.19 ⫺0.02 ⫺0.38** — ⫺0.08 ⫺0.24

— OR ⫽ 1.12 ⫺0.17 ⫺0.00 ⫺0.29** — ⫺0.05 ⫺0.29**

OR ⫽ 1.04 ⫺0.15**

OR ⫽ 1.35 0.03

a For continuous measures, the presented numbers are ␤’s; for dichotomous measures, the presented numbers are odds ratios. b Negative ␤’s or odds ratios ⬍1 indicate lower scores for the treatment group (a program effect in the predicted direction). c All responses are from follow-up 1 (3 months after intervention). All responses are from adolescents. * P ⬍ 0.05. ** P ⬍ 0.01.

Table 7 presents the relationships between the potential mediators, measured by adolescent report, and adolescent smoking and drinking. Here, too, there are many more significant relationships than when parent reports are used to measure the mediator variables, as shown by comparison with Table 4. Positive change on all of the global and most of the substance-specific family characteristics and both adolescent cognition variables was associated with decreased smoking and drinking by adolescents. We next assessed mediation. In the non-Hispanic white sample, parental support, adolescent expectations about the negative consequences of smoking, and adolescent intentions to smoke met the necessary conditions to qualify as potential mediators of the program effect on adolescent smoking. Comparison of the odds ratio for the program effect on smoking, unadjusted (1.59, P ⫽ 0.004, lower bound confidence limit 1.19) and adjusted for the mediators (1.45, P ⫽ 0.026, lower bound confidence limit 1.06), shows that the adjusted odds ratio is only slightly smaller, suggesting that the program effect on prevalence of smoking among nonHispanic whites was not primarily due to changes produced by the program on the mediator variables.

In the full sample, parental support, family rules about drinking, discussion of nonfamily influences on drinking, and adolescent intentions to drink were identified as possible mediator variables of the program effect on adolescent drinking. Comparison of the odds ratios for the program effect on drinking, unadjusted (1.38, P ⫽ 0.02, lower bound confidence limit 1.07) and adjusted (1.34, P ⫽ 0.04, lower bound confidence limit 1.02) for the mediators, shows a trivial difference, suggesting that program effects on the mediator variables did not explain the effect on the prevalence of drinking. DISCUSSION

The success of drug use prevention programs is told by the presence or absence of effects on drug use, but identification of mediating processes is key to understanding how program effects are achieved and thus to suggesting how programs can be improved [24, 25]. When a significant change in adolescent drug use is accompanied by significant change in one or more mediator variables, it is possible that the mediator variables are the cause of the program effect but this cannot be determined without direct testing as was done here [45]. Although examination of program effects on intermediate variables is becoming more common in evaluation of adolescent drug use prevention programs, simultaneous analysis of program effects on intermediate and outcome variables to determine mediation remains less common [19, 45]. The importance of mediation analysis is illustrated by our findings: Had we not conducted the mediation analysis, we would have made erroneous conclusions about the mechanisms through which the program influenced adolescent smoking and drinking. Specifically, the conclusion from our analysis of program effects on intermediate variables is that the program was successful in changing several substancespecific aspects of the family environment. According to parents, families exposed to Family Matters were more likely to set rules about tobacco and alcohol use, provide encouragement not to smoke, and talk about peer and media influences on alcohol use. Similar findings were obtained from adolescents. Had we stopped our analysis here, our findings could have suggested the importance of refining the program content to focus more fully on substance-specific family characteristics—such as tobacco and alcohol-directed communication and rule setting—and to eliminate or give less emphasis to content focused on changing global parenting practices. These actions would have been premature, and the possibility that they might have been undertaken underscores the need for full mediation analysis of intervention effects. Mediators were not identified by our analyses because the family and adolescent variables influenced

343

ADOLESCENT TOBACCO AND ALCOHOL USE MEDIATORS

TABLE 6 Associations between Change in Family Characteristics at Follow-up 1 and Change in Adolescent Cognitions at Follow-up 1, Adolescent Reports Tobacco model Non-Hispanic whites (N ⫽ 791)

Family characteristics Global family Supervision Support Communication Involvement Substance-specific Expected consequences Parental attitude Parental encouragement Parent use Rules about use Monitoring Availability in home Nonfamily influences on use

Alcohol model Full sample (N ⫽ 1,014)

Expect negative consequences of usea (odds ratio)

Intentions to useb (␤)

Expect negative consequences of usea (odds ratio)

Intentions to useb (␤)

1.13** 1.27** 1.27** 1.16

0.06** 0.07* 0.07** 0.14**

1.06* 1.08 1.12** 1.04

0.03** 0.08** 0.06** 0.10**

— 3.34** 1.09 1.52 1.07 — 1.17 1.07

— 0.28** 0.02 0.19* 0.02 — 0.16** 0.04**

— 2.12** 1.04 1.21 0.99 — 1.36** 1.06

— 0.40* 0.04** 0.09 0.04** — 0.28** 0.07**

a The Expect negative consequences measures are dichotomous, and the presented numbers are bivariate odds ratios obtained from logistic regression. Odds ratios ⬎1 indicate that positive changes in family characteristics were associated with positive changes in adolescent cognitions. b The Intentions measures are continuous, and the presented numbers are bivariate ␤’s obtained from regression models. Positive ␤ ’s indicate that positive changes in family characteristics were associated with positive changes in adolescent cognitions. * P ⬍ 0.05. ** P ⬍ 0.01.

by the program tended not to be the same family and adolescent variables that influenced adolescent smoking and drinking. Without significant paths from the program to mediators, and mediators to outcome, mediation cannot be present. Why were the paths not present? Perhaps the proposed mediators were poorly measured, perhaps our analyses failed to capture the appropriate time period for change in mediators, or perhaps we failed to adequately conceptualize the appropriate mediators. We address each of these possibilities in turn. We assessed measurement quality in two ways: replication of the mediation analyses with measures of family mediators derived from factor analysis and replication of the mediation analyses when substituting adolescent reports to measure family mediators. We began with parent report measures of the family mediators to provide the strictest test of mediation by using a different source for the mediator variables (parent) than for the behavioral outcomes (adolescent). These measures were based on our a priori selection of items to operationalize each construct. The factor analysisderived parent report measures allowed testing of different combinations of items that might be more informative than the sets of items we specified to measure

each family construct. However, the factor analysisderived measures were shown to be quite similar to the original parent report measures and the mediation results did not differ. The adolescent report measures had better reliability, as evidenced by higher internal consistency, and may have had better validity than either type of parent report measure. Evidence for the validity of the measures is the strong pattern of expected relationships between the proposed mediator variables and adolescent smoking and drinking, although part of the association could have been due to the shared measurement source. Despite the improved psychometric properties, results using the adolescent report measures were no more informative in identifying the program mediators than those using either type of parent report measure. All together, the results suggest that measurement issues appear to be a weak explanation for our lack of mediation findings. Still, other methods of measurement often used in research on family functioning, such as observation of parent–child interactions, may have been useful [46]. Such methods would have been impractical, however, with our national sample and data collection by telephone. As another possibility, perhaps our analysis approach did not capture the appropriate time period for when

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TABLE 7 Global and Substance-Specific Family Characteristic and Adolescent Cognition Effects on Adolescent Smoking and Drinking, Adolescent Reports Regression coefficientsa,b

Outcomec Global family Supervision Support Communication Involvement Substance-specific Expected consequences Parental attitude Parental encouragement Parent use Rules about use Monitoring Availability in home Nonfamily influences on use Adolescent cognitions Expected consequences Intentions to use

Tobacco model Non-Hispanic whites (N ⫽ 791)

Alcohol model Full sample (N ⫽ 1,014)

0.18** 0.34** 0.17** 0.31**

0.19** 0.34** 0.17** 0.36**

— 0.66** 0.10** 0.55** 0.02 — 0.18** 0.05

— 1.09** 0.16** 0.44** 0.12** — 0.48** 0.24**

1.82** 0.85**

1.34** 0.20**

a The coefficients are from GEE models in which smoking and drinking behavior were measured at both follow-up 1 (3 months after intervention) and follow-up 2 (12 months after intervention). b Positive coefficients indicate that positive change in the mediator was associated with less adolescent smoking or drinking. c The mediators are difference scores from baseline to follow-up 1 (3 months after intervention). ** P ⬍ 0.01.

change in the program mediators took place. We measured change in the mediator variables from baseline to follow-up 1 and change in the behavioral variables from baseline through both follow-up 1 and follow-up 2. It could be that the effect of the mediators on the behavioral variables occurred between follow-up 1 and followup 2 or that change in the mediators occurred concurrently with change in the behavioral variables. We did not test these possibilities with alternative models, however, because of increased ambiguity in identifying whether change in the mediators occurred before or after change in adolescent smoking or drinking. With respect to our conceptualization of the mediators, perhaps we did not identify and measure the appropriate mediator variables. The possibility of omitting relevant family variables runs counter to the etiologic evidence supporting the family factors targeted by the program and the attention given to measurement of a broad array of family factors. Nevertheless, it is possible that the behavioral effects occurred through some more global change in the family environment or family relationships that was not reflected in

the specific indicators. Or, perhaps the program influenced adolescent characteristics other than the two cognitive factors we measured. For example, adolescents’ beliefs about family and peer acceptance of drug use and their confidence in their ability not to use drugs have been linked with drug use [12, 14, 47, 48]. Our respecification of the model using adolescent reports of family characteristics resulted in measures of adolescents’ perceptions of their parents’ attitudes toward smoking and drinking and many other potential family influences, but these measures did not account for program effects. Perhaps program impact on adolescent beliefs about self-efficacy not to smoke or drink or perceptions of the acceptability of peer use—both of which reasonably might have been impacted by program activities—account for program effects on behavior. Identification of additional mediating processes remains for speculation, as they cannot be tested with the data we collected. Although we cannot conclude that Family Matters caused the observed impacts on prevalence of adolescent smoking and drinking through the expected changes in the family, our findings suggest that an important area for future research is determining the types of family change that can be achieved in universal programs. Of specific interest is whether, owing to the modest intensity of universal programs, change in global parenting practices is more difficult to achieve than change in how parents specifically interact with their children about substance use. Global family characteristics, such as the quality of the parent–child relationship, may represent stable properties of relationships less amenable to change than substance-specific family characteristics, such as parents talking with their adolescent about the consequences of smoking and drinking. Primary evidence for the ability to produce change in global parenting practices comes from programs implemented with higher risk families and using more intensive intervention with direct contact between program providers and parents [1, 2]. This level of effort may be difficult to achieve in universal programs and may explain why Family Matters appears more successful at changing substance-specific than global family characteristics. Similar to our findings, Spoth and colleagues, who rigorously evaluated the effects of two family-based interventions with general population samples, found stronger evidence for program effects on specific than on global family characteristics [3]. Knowing what is reasonable to be achieved in universal prevention programs involving the family is an important area for continued research. As well, continued development and evaluation of universal prevention programs implemented with families is warranted. Family Matters is one of only a few universal family-based programs that has been rigorously evaluated. If the prevalence of adolescent tobacco

ADOLESCENT TOBACCO AND ALCOHOL USE MEDIATORS

and alcohol use is to be decreased beyond current levels, interventions focused on all the social environments of adolescents, including the family, are indicated [49–51]. For family-based programs as for any other type of drug use prevention program, mediation analysis is a necessary adjunct to program development.

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ACKNOWLEDGMENT We thank Margaret Ostafin for assistance in preparing the manuscript.

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