Predictors and moderators of psychological changes during the treatment of adolescent bulimia nervosa

This study examined predictors of psychological change among 80 adolescents with bulimia nervosa (BN) participating in a randomized-controlled trial comparing family-based treatment (FBT) to supportive psychotherapy (SPT). Psychological outcomes (cognitive eating disorder pathology, depression, and self-esteem) were explored at baseline, post-treatment, and 6-month follow-up. Multi-level growth models examined predictors of rate of change in psychological outcomes and moderators of treatment effects. All psychological outcomes improved through 6-month follow-up (moderate to large effect sizes) across both treatments. Overall, few significant predictors were identified. Older adolescents had faster change in self-esteem relative to younger adolescents (p = 0.03). Adolescents taking psychotropic medication at baseline had faster change in eating concerns relative to adolescents not taking medication (p = 0.02). Age (p = 0.02) and baseline purging severity (p = 0.03) moderated the relationship between treatment condition and change in eating concerns, where younger adolescents and individuals with high baseline purging had greater change when treated with FBT relative to SPT. Age and purging did not significantly moderate change in other psychological outcomes. Bulimic symptom improvement did not predict change in psychological symptoms. Generally, FBT and SPT were equally efficacious with respect to psychological improvement, although FBT may be more efficacious in younger adolescents and those with more frequent purging.