Moderators and mediators of outcome in Internet-based indicated prevention for eating disorders.

The objective of this study was to investigate moderators and mediators of the effect of an indicated prevention program for eating disorders (ED) on reduction of dysfunctional attitudes and specific ED symptoms. 126 women (M age = 22.3; range 18-33) reporting subthreshold ED symptoms were randomized to the Student Bodies™+ (SB+) intervention or an assessment-only control condition. Assessments took place at pre-intervention, mid-intervention (mediators), post-intervention, and 6-month follow-up. Mixed effects modeling including all available data from all time points were used for the data analysis. Intervention effects on the reduction of binge rate were weaker for participants with higher baseline BMI and for participants with a lower baseline purge rate. Intervention effects on reduction of eating disorder pathology were weaker for participants with higher baseline purge rate and with initial restrictive eating. No moderators of the intervention effect on restrictive eating were identified. An increase in knowledge mediated the beneficial effect of SB+ on binge rate. The results suggest that different moderators should be considered for the reduction of symptoms and change in attitudes of disturbed eating and that SB+ at least partially operates through psychoeducation.