How Did It Work? Who Did It Work for? Mediation in the Context of a Moderated Prevention Effect for Children of Divorce.

Abstract

This study presents a reanalysis of data from an effective preventive intervention for children from divorced families (S. A. Wolchik et al., 2000) to test mediation of program effects. The study involved 157 children, age 9 -12 years, who were randomly assigned to a parenting program or a literature control condition. Program effects to reduce posttest internalizing problems were mediated through improvement in mother-child relationship quality. Program effects to reduce externalizing problems at posttest and 6 months were mediated through improvement in posttest parental methods of discipline and mother-child relationship quality. The study also describes a new methodology to test mediation of Program ϫ Baseline Status interactions. Analyses demonstrate mediation effects primarily for children who began the program with poorer scores on discipline, mother-child relationship quality, and externalizing problems. Health Grant R01 MH057013-01A1 to evaluate a preventive intervention for children of divorce, and Public Health Service Grant DA09757 for development and application of methods to assess mediation. We thank the mothers and children for their participation as well as the group leaders for their careful and thoughtful delivery of the program.

Addressing Moderated Mediation Hypotheses: Theory, Methods, and Prescriptions

“…In models like Models 1 to 5, the conditional indirect effect may be probed for significance using methods directly analogous to those used to probe significant interaction effects in regression (Aiken & West, 1991;Morgan-Lopez, 2003;Muller et al, 2005;Tein, Sandler, MacKinnon, & Wolchik, 2004). This method requires that the researcher have in mind a few values of the moderator for which it would be meaningful to examine the magnitude and significance of the indirect effect.…”

“…This method requires that the researcher have in mind a few values of the moderator for which it would be meaningful to examine the magnitude and significance of the indirect effect. Muller et al (2005) and Tein et al (2004), in a clever extension of a procedure described by Aiken and West (1991), Darlington (1990), and Judd and McClelland (1989), further outline a procedure whereby the researcher may center the moderator at conditional values and use key regression weights to interpret mediation effects as if the model were a simple mediation model. Our extension of the J-N technique to conditional indirect effects has the advantage that it does not require choosing possibly arbitrary conditional values.…”

“…We restrict attention to the case when there exists an indirect effect of X on Y through M (the simplest form of indirect effect), with the pertinent question regarding whether mediation exists for different conditional values of W . For example, Tein et al (2004) examined whether self-efficacy mediated the effect of cultural norms on cigarette use differently depending on the number of peers who smoked. Hodges and Perry (1999) demonstrated that children's internalizing and physical weakness influence physical and verbal victimization, and that victimization in turn influences future internalizing and peer rejection.…”

Methods for testing theory and evaluating impact in randomized field trials: Intent-to-treat analyses for integrating the perspectives of person, place, and time

“…Variation by individual level risk is also important in selective and indicated interventions, especially as this can help determine an optimal cutoff in risk below which an intervention has limited effect (Tein et al, 2004). Alternatively, we may decide to modify an intervention so that its impact is improved over a wider range of risk.…”

“…Most importantly, they differ from efficacy trials on the degree of control placed on implementation of the intervention. They are designed to address questions other than those of pure efficacy, and they often assess both mediator and moderator effects (Krull and MacKinnon, 1999;MacKinnon and Dwyer, 1993;MacKinnon et al, 1989;Tein et al, 2004). Also, they often differ from many traditional trials by the level at which randomization occurs as well as the choice of target population.…”