Rapid response is predictive of treatment outcomes in a transdiagnostic intensive outpatient eating disorder sample: a replication of prior research in a real-world setting

Objective: There is a growing call to identify specific outcome predictors in real-world eating disorder (ED) treatment settings. Studies have implicated several ED treatment outcome predictors [rapid response (RR), weight suppression, illness duration, ED diagnosis, and psychiatric comorbidity] in inpatient settings or randomized controlled trials of individual outpatient therapy. However, research has not yet examined outcome predictors in intensive outpatient programs (IOP). The current study aimed to replicate findings from randomized controlled research trials and inpatient samples, identifying treatment outcome predictors in a transdiagnostic ED IOP sample. Method: The current sample comprised 210 consecutive unique IOP patient admissions who received evidence-based ED treatment, M(SD)_Duration = 15.82 (13.38) weeks. Weekly patient measures of ED symptoms and global functioning were obtained from patients’ medical charts. Results: In relative weight analysis, RR was the only significant predictor of ED symptoms post treatment, uniquely accounting for 45.6% of the predicted variance in ED symptoms. In contrast, baseline ED pathology was the strongest unique predictor of end-of-treatment global functioning, accounting for 15.89% of predicted variance. Baseline factors did not differentiate patients who made RR from those who did not. Conclusions: Consistent with findings in more controlled treatment settings, RR remains a robust predictor of outcome for patients receiving IOP-level treatment for EDs. Future work should evaluate factors that mediate and moderate RR, incorporating these findings into ED treatment design and implementation. Level of evidence: Level IV, uncontrolled intervention.