Jennifer L. Krull

Equivalence of the Mediation, Confounding and Suppression Effect

This paper describes the statistical similarities among mediation, confounding, and suppression. Each is quantified by measuring the change in the relationship between an independent and a dependent variable after adding a third variable to the analysis. Mediation and confounding are identical statistically and can be distinguished only on conceptual grounds. Methods to determine the confidence intervals for confounding and suppression effects are proposed based on methods developed for mediated effects. Although the statistical estimation of effects and standard errors is the same, there are important conceptual differences among the three types of effects.

Multilevel Modeling of Individual and Group Level Mediated Effects.

This article combines procedures for single-level mediational analysis with multilevel modeling techniques in order to appropriately test mediational effects in clustered data. A simulation study compared the performance of these multilevel mediational models with that of single-level mediational models in clustered data with individual- or group-level initial independent variables, individual- or group-level mediators, and individual level outcomes. The standard errors of mediated effects from the multilevel solution were generally accurate, while those from the single-level procedure were downwardly biased, often by 20% or more. The multilevel advantage was greatest in those situations involving group-level variables, larger group sizes, and higher intraclass correlations in mediator and outcome variables. Multilevel mediational modeling methods were also applied to data from a preventive intervention designed to reduce intentions to use steroids among players on high school football teams. This example illustrates differences between single-level and multilevel mediational modeling in real-world clustered data and shows how the multilevel technique may lead to more accurate results.

Positive affect and the experience of meaning in life

Six studies examined the role of positive affect (PA) in the experience of meaning in life (MIL). Study 1 showed strong relations between measures of mood, goal appraisals, and MIL. In multivariate analyses, PA was a stronger predictor of MIL than goal appraisals. In Study 2, the most consistent predictor of the experience of meaning in a day was the PA experienced that day. Later, global MIL was predicted by average daily PA, rather than average daily MIL. Study 3 demonstrated no prospective relations between measures of MIL and PA over 2 years. In Study 4, priming positive mood concepts enhanced MIL. In Study 5, manipulated positive mood enhanced ratings of MIL for those who were not given an attributional cue for their moods. In Study 6, PA was associated with a high level of distinction between meaningful and meaningless activities. Results indicate that positive moods may predispose individuals to feel that life is meaningful. In addition, positive moods may increase sensitivity to the meaning-relevance of a situation.

Multilevel Mediation Modeling in Group-Based Intervention Studies.

This article proposes and evaluates a method to test for mediation in multilevel data sets formed when an intervention administered to intact groups is designed to produce change in individual mediator and outcome variables. Simulated data of this form were used to compare ordinary least squares (OLS) and two multilevel estimators of the mediated effect. OLS and multilevel standard error approximations were also evaluated and recommendations given for optimal estimator choice. These methods were applied to data from an existing substance use intervention to show the impact multilevel mediation modeling can have on the conclusions drawn from real-world evaluation studies.

Cancer Risk Reduction in Mexican American Women: The Role of Acculturation, Education, and Health Risk Factors

This article describes a two-factor schema for the development of culturally appropriate cancer risk reduction interventions for Mexican American women. Regarding this approach, risk factors for two major cancer areas are reviewed: cigarette smoking and obesity/diet. We first describe a schema that facilitates the planning of strategies associated with preferred health interventions and preventive approaches for cancer risk reduction with Mexican American and other Latino/Hispanic persons. This schema examines Acculturation and Education as key factors that should be considered in developing health education messages and interventions that are culturally and educationally appropriate to the identified subpopulations of Hispanics in terms of language and informational content of the message and in terms of psychological factors related to health behavior change. Empirical data from a community sample is presented for the purpose of illustrating the validity of this schema.

Mediating mechanisms in a program to reduce intentions to use anabolic steroids and improve exercise self-efficacy and dietary behavior.

This study investigated the mediating mechanisms responsible for the effects of a program designed to reduce intentions to use anabolic steroids, improve nutrition, and increase strength training self-efficacy. Fifteen of 31 high school football teams (N = 1,506 players at baseline) in Oregon and Washington were assigned to receive the intervention. The multicomponent program addressed the social influences promoting ergogenic drug use and engaging students in healthy nutrition and strength training alternative behaviors. Although the results differed across the three dependent variables, the program appeared to work by changing team norms. Unlike prevention of other drugs, changes in knowledge and perceived severity were mediators of program effects in this study.

Motivational pathways to alcohol use and abuse among Black and White adolescents

Using data from a biracial community sample of adolescents, the present study examined trajectories of alcohol use and abuse over a 15-year period, from adolescence into young adulthood, as well as the extent to which these trajectories were differentially predicted by coping and enhancement motives for alcohol use among the 2 groups. Coping and enhancement motivations (M. L. Cooper, 1994) refer to the strategic use of alcohol to regulate negative and positive emotions, respectively. Results showed that Black and White youth follow distinct alcohol trajectories from adolescence into young adulthood and that these trajectories are differentially rooted in the regulation of negative and positive emotions. Among Black drinkers, coping motives assessed in adolescence more strongly forecast differences in alcohol involvement into their early 30s, whereas enhancement motives more strongly forecast differences among White drinkers. Results of the present study suggest that different models may be needed to account for drinking behavior among Blacks and Whites and that different approaches may prove maximally effective in reducing heavy or problem drinking among the 2 groups.

Changes in heavy drinking over the third decade of life as a function of collegiate fraternity and sorority involvement: a prospective, multilevel analysis.

Although affiliation with a fraternity or sorority is an important risk factor for heavy drinking, recent research indicates that this risk may be limited to the college years. Random coefficient growth modeling was used to track changes in patterns of heavy drinking over the course of 11 years as a function of gender and collegiate Greek involvement (N=318). Overall, greater cumulative exposure to the Greek system led to increased heavy drinking during the college years, particularly among men. Shortly after leaving college, heavy drinking levels dropped markedly and remained low through approximately age 30. Inclusion of peer alcohol use norms in the model reduced the influence of Greek involvement. Implications for models of heavy drinking and health risks are discussed.

The Relation of Personality to Alcohol Abuse/Dependence in a High‐Risk Sample

The current study had two goals. The first goal was to test the mediational role of young adult personality in the relation between parental alcoholism and young adult alcoholism. The second was to examine the associations between personality and alcohol use motives and reasons to limit drinking in order to explore possible mechanisms by which personality may influence alcohol abuse/dependence. Multilevel modeling techniques were used to analyze data obtained from a community sample of young adult children of alcoholics and demographically matched controls. Results revealed that young adult neuroticism and agreeableness each, in part, mediated the effect of parental alcoholism on young adult alcoholism. Moreover, individuals high in neuloticism reported stronger coping motives to use alcohol, individuals low in agreeableness reported stronger coping motives and weaker upbringing reasons to limit drinking, and individuals low in conscientiousness reported stronger coping and enhancement motives to use alcohol, and weaker performance reasons to limit drinking.

Blue-Collar Scholars?: Mediators and Moderators of University Attrition in First-Generation College Students

Many college entrants’ parents do not have college degrees. These entrants are at high risk for attrition, suggesting it is critical to understand mechanisms of attrition relative to parental education. Moderators and mediators of the effect of parental education on attrition were investigated in 3,290 students over 4 years. Low parental education was a risk for attrition; importantly, college GPAs both moderated and mediated this effect, and ACT scores, scholarships, loans, and full-time work mediated this effect. Drug use, psychological distress, and few reported academic challenges predicted attrition, independent of parental education. These findings might inform interventions to decrease attrition.