Testing mediators hypothesized to account for the effects of a dissonance-based eating disorder prevention program over longer term follow-up.

Because eating disorders are marked by functional impairment and increased risk for numerous health problems (Stice, Marti, Shaw, & Jaconis, 2009a; Wilson, Becker, & Heffernan, 2003), it is vital to develop effective prevention programs. Marked support has emerged for a dissonance-based eating disorder prevention program, wherein young women critique the thin-ideal espoused for women, which theoretically produces cognitive dissonance that causes participants to reduce thin-ideal internalization. Reduced thin-ideal internalization in turn putatively reduces body dissatisfaction, weight control efforts, and negative affect, thereby reducing eating disorder symptoms. Efficacy trials show that this intervention has reduced eating disorder risk factors (thin-ideal internalization, body dissatisfaction, and negative affect), eating disorder symptoms, and risk for future onset of eating disorders relative to alternative interventions and assessment-only controls, with some effects persisting for 3-years (Becker, Smith, & Ciao, 2006; Mitchell, Mazzeo, Rausch, & Cooke, 2007; Parez, Becker, & Ramirez, 2010; Stice, Marti, Spoor, Presnell, & Shaw, 2008; Stice, Shaw, Burton, & Wade, 2006). To date, only one controlled trial has tested the meditational processes hypothesized to produce intervention effects, which is important for testing the intervention theory of prevention programs. Stice, Presnell, Gau, and Shaw (2007) found that relative to an expressive writing control condition, the dissonance intervention produced greater reductions in thin ideal internalization as well as greater reductions in body dissatisfaction, self-reported dieting, negative affect, and eating disorder symptoms, that change in thin-ideal internalization correlated with change in the other outcomes, that intervention effects became weaker when change in thin-ideal internalization was controlled, and that dissonance participants were more likely to show meaningful change (.5 SD) in thin-ideal internalization before they showed an equivalent degree of change in the other outcomes. The fact that change in thin-ideal internalization partially mediated the effects of this intervention on change in eating disorder symptoms prompted Stice et al (2007) to suggest that body dissatisfaction may also play a role in mediating the effects of the intervention on symptom reduction. An uncontrolled trial provided evidence that changes in both thin-ideal internalization and body dissatisfaction partially mediated the effects of this intervention on reductions in eating disorder symptoms (Seidel, Presnell, & Rosenfield, 2009). Although these two studies provided support for the meditational model for this prevention program, both focused on change during the intervention delivery phase. As the dissonance intervention produces effects on outcomes that persist over multiple years, it seems important to test whether change in the hypothesized mediators accounts for longer-term intervention effects. Thus, we tested whether reductions in thin-ideal internalization and body dissatisfaction mediated the effects of the dissonance prevention program on change in eating disorder symptoms through 1-year follow-up. Another unique aspect of the present report is that data were drawn from an effectiveness trial rather than an efficacy trial, which test whether interventions produce effects when delivered by endogenous providers (e.g., school counselors) who are not closely supervised under real world conditions with heterogeneous populations. The current trial found that when high school counselors and nurses recruited students and delivered the intervention, it produced significantly greater reductions in thin-ideal internalization, body dissatisfaction, dieting, and eating disorder symptoms, but not negative affect, through 1-year follow-up relative to educational brochure controls (Stice, Rohde, Gau, & Shaw, 2009b). The present meditational model posits that the intervention reduces thin-ideal internalization that results in improved body dissatisfaction and consequent reduction in eating disorder symptoms. Thus, we tested whether change in thin-ideal internalization partially mediates the effects of the intervention on change in body dissatisfaction and eating disorder symptoms and whether change in body dissatisfaction partially mediates the effects of the intervention on change in symptoms.