What Makes Personalized Treatment Work? Mechanisms of Change in Personalized Treatment for Eating Disorders: A Proof-of-Concept Study.

Eating disorders (EDs) are severe illnesses with high rates of mortality; however, evidence-based ED treatments only work for 50% of individuals. Part of the reason that treatments do not work is that EDs are highly heterogenous, signifying a need to personalize treatment. As such, idiographic (i.e., one-person) methods have been used to develop personalized treatment for EDs. Our team demonstrated that a new Transdiagnostic Network-Informed Personalized Treatment (T-NIPT-ED) that uses idiographic modeling to select evidence-based treatment modules for EDs was feasible, acceptable, and decreased ED and cooccurring symptoms (e.g., depression). However, it remains unknown how T-NIPT-ED works and if T-NIPT-ED intervenes effectively on the hypothesized mechanisms of change. The current study (N = 75 with an ED) tested if central symptoms (i.e., hypothesized mechanisms of change) assessed for 15 days (5 times a day; 75 timepoints at two times of day [150 timepoints]) pre- and posttreatment with ecological momentary assessment changed through treatment. We used mixed effects linear regression to test (a) if symptoms in broad categories of affect, cognitions, behavior, comorbid conditions, and physiology changed from pre- to posttreatment and (b) if specific symptoms matched to corresponding evidence-based treatment modules changed with treatment. We found that if a participant had a central symptom in an affective or behavioral category, overall affect and behaviors decreased respectively. We also found that participants with the following central symptoms targeted in treatment evidenced reductions in these mechanisms: shame, self-criticism, body checking, rumination, overvaluation of weight/shape, and guilt. Our results suggest that T-NIPT-ED is effective at reducing ED-related affect and behaviors. Furthermore, these data suggest that several modules targeted at specific mechanisms hypothesized to maintain EDs are effective in the context of personalized treatment.