From Predictors to Processes: Exploring the Early Response Effect in the Psychological Treatment of Eating Disorders

Treatment outcomes for people with eating disorders remain poor, with only around half of those who receive recommended treatment achieving full recovery. Researchers have therefore sought to identify which factors best predict who will benefit most from psychotherapy. One of the strongest predictors is the early response effect: people who show meaningful symptomatic improvement in the first few sessions of therapy are more likely to recover by the end of treatment.
Despite this, it is often assumed that people with severe and enduring eating disorders (SE-ED) respond poorly to treatment and require alternative approaches. The first chapter of this thesis reviewed the evidence behind this assumption. Fourteen studies used the term SE-ED, yet none agreed on a consistent definition. Across 35 studies examining whether duration or severity predict treatment outcomes, neither factor consistently related to recovery. Three studies found that early response was not influenced by severity or chronicity of the eating disorder. Taken together, these findings suggest that early response may be a more reliable predictor of recovery than either chronicity or severity.
Building on this insight, the second chapter presents an empirical study examining which specific symptoms change early in treatment. Data from 232 people receiving outpatient psychotherapy for eating disorders were analysed using a supervised machine learning method called Bayesian network analysis. This identified six symptoms most strongly linked to recovery: avoiding others seeing one’s body, feeling “fat”, preoccupation with food or calories, fears of overeating, feeling unhappy with one’s body shape, and following strict dietary rules. Early improvements in these areas during the first four sessions of therapy were strong predictors of recovery. These findings indicate that focusing on these six areas during the initial sessions of treatment may help clinicians better support recovery for people with eating disorders.