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PSYC*3690 Article 7.pdf

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Department
Psychology
Course
PSYC 3690
Professor
Benjamin Gottlieb
Semester
Winter

Description
Article #: 7 Title: Testing Mediators of Intervention Effects in Randomized Controlled Trials: An Evaluation of Two Eating Disorder Prevention Programs Goals - of the article: investigate mediators hypothesized to account for effects of 2 eating disorder prevention programs - the goal of the first prevention program was to reduce their thin-ideal internalization to decrease eating disorder risk factors and bulimic symptoms - the goal of the second prevention program was to promotes lasting healthy changes to dietary intake and physical activity as a way of achieving a healthy body weight and body satisfaction which decreases eating disorder risk factors and symptoms Who Benefits? (Target Audience) - students who have body image concerns Universal, Selective, or Indicated - Indicated because students had to endorse body image concerns during a telephone screen - each was screened and found to be at risk Primary, Secondary, Tertiary - primary - none of the girls already had an established disorder Risk and Protective Factors - risk = body image concerns Measures of Data Collection (what is measured, # of times, and how) - data was collected 4 times once per week for 4 weeks, tested mediation - thin-ideal internalization was measured with an eight-item Ideal-Body Stereotype Scale-Revised - health eating was measured by 4 items assessing healthy eating behaviours Intervention Strategies? - dissonance-based program = voluntarily engage in verbal, written and behavioural exercises in which they critiqued the thin ideal - health weight management program = encouraged to make healthy and lasting changes to their diet and physical activity level as a way of balancing their energy needs with energy intake and thereby achieving a healthier weight satisfaction Results (what did the program accomplish) - dissonance improved body dissatisfaction, reduced negative affect and bulimic symptoms - health weight produced reductions in body dissatisfaction, dieting, negative affect and bulimic symptoms Limitations - reliance on self-report data might have been biased - limited data on the reliability and validity of healthy eating and physical activity measures - design does not permit us to definitively rule out the possibility of bidirectional effects between change in the mediators and change in the outcomes - did not assess nonspecific factors that may partially account for intervention effects Other Important Facts 3 Box Model: Dissonance Dissonance-Based Model - reductions in thin-ideal - improved body internalization dissatisfaction, reduced negative affect and bulimic symptoms 3 Box Model: Healthy Weight Management Healthy Weight Model - improvements in healthy - reductions in body eating and physical dissatisfaction, dieting, activity negative affect and bulimic symptoms Monday, Jan 21, 2012 7. Testing Mediators of Intervention Effects in Randomized Controlled Trials: An Evaluation of Two Eating Disorder Prevention Programs Abstract - the authors investigated mediators hypothesized to account for the effects of 2 eating disorder prevention programs using data from 355 adolescent girls who were randomized to a dissonance or a healthy weight intervention or an active control condition - the dissonance intervention produced significant reductions in out comes (body dissatisfaction, dieting, negative affect) and the mediator (thin-ideal internalization), change in the mediator correlated with change in outcomes and usually occurred before change in outcomes, and intervention effects became significantly weaker when change in the mediator was patrolled, providing support for the hypothesized mediators and this new approach to testing mediation in randomized trials - findings provide somewhat less support of the hypothesis that change in healthy eating and exercise would mediate the healthy weight intervention effects - 10% of adolescent girls experience threshold or subthreshold eating disorders - only 6 prevention programs have produced significant reductions in current or future symptoms and only 2 produced effects that replicated across labs - the first intention is a dissonance-based program, in which at-risk girls with body image concerns who have internalized the thin ideal voluntarily engage in verbal, written and behavioural exercises in which they critique this ideal - this results in psychological discomfort that motivates them to reduce their thin-ideal internalization to restore cognitive consistency - results in significantly greater reductions in thin-ideal internalization, body dissatisfaction, negative affect and bulimic symptoms - the second intervention is a health weight management program, which promotes lasting healthy changes to dietary intake and physical activity as a way of achieving a healthy body weight and body satisfaction among at-risk girls with body image concerns - produces reductions in body dissatisfaction, dieting, negative affect, and bulimic symptoms - both have targeted at-risk girls because selected prevention programs tend to produce larger effects than universal programs - this study initiated a large efficacy trial of these 2 intentions and addressed limitations - (a) compared our interventions with an active control intervention to rule out the possibility that intervention effects were due to demand characteristics, expectancies, or attention, (b) used blinded diagnostic interviews to assess eating pathology, c(c) used long-term follow-up and (d) used a larger and more ethnically diverse sample relative to prior trials - 481 adolescent girls were randomly assigned to the dissonance intervention, the healthy weight intervention, an expressive writing active control condition, or an assessment-only control condition - the dissonance participants showed greater reductions in eating disorder risk factors and bulimic symptoms - healthy weight participants showed greater reductions in these outcomes than expressive writing and assessment-only participants - participants in both interventions also showed lower binge eating and obesity onset and decreased mental health service utilization - report seeks to test hypotheses regarding the mediators that theoretically account for the intervention effects - mediation analyses provide a test of the mechanisms that putatively underlie intervention effects - test whether the mediators that are theoretically specific to an intervention account for the intervention effects - a previous study found that a change in body dissatisfaction partially mediated the effects of the intervention on change in depressive and bulimic symptoms - hypothesis: reductions in thin-ideal internalization would mediate the effects of the dissonance intervention, vs the expressive writing control condition, on reductions in body dissatisfaction, dieting, negative affect and bulimic symptoms - hypothesis: improvements in healthy eating and physical activity would mediate the effects of the healthy weight intervention, vs the expressive writing control condition, on reductions in body dissatisfaction, negative affect and bulimic symptoms - improvements in dietary intake and activity were also expected to reduce negative affect - secondary aim of this report is to propose a more rigorous test of mediation for randomized trials - propose the strongest case for mediation will be made when 5 conditions are satisfied: 1. Participants in the intervention condition show significantly greater decreases on the outcome over time than controls 2. Participants in the intervention condition show significantly greater decreases on the mediator over time than controls 3. Change in the mediator over time is significantly correlated with change in the outcome over time in the intervention condition 4. The predictive effect of intervention condition on change in the outcome, controlling for change in the mediator is significantly reduced or eliminated, relative to when the outcome is regressed only on intervention condition 5. Meaningful change in the mediator occurs before meaningful change in the outcome significantly more frequently than would be expected on the basis of change in the intervention condition - it is vital to document that change in the mediator precedes change in the outcome to establish mediation - also tested whether there was evidence of specificity for the putative mediators for each intervention - tested for mediation from pre- to po
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