Abstract
BACKGROUND: Cognitive-behavioral therapy for avoidant/restrictive food intake disorder (ARFID; CBT-AR) theoretically targets three prototypic motivations (sensory sensitivity, lack of interest/low appetite, fear of aversive consequences), aligned with three modularized interventions. As an exploratory investigation, we: (1) evaluated change in candidate mechanisms in relationship to change in ARFID severity, and (2) tested if assignment (vs. not) to a module resulted in larger improvements in the corresponding mechanism. METHOD: Males and females (N = 42; 10-55 years) participated in an open trial of CBT-AR. RESULTS: Decreases in scaled scores for each candidate mechanism had medium to large correlations with decreases in ARFID severity-sensory sensitivity: -0.7 decrease (r = .42, p = .01); lack of interest/low appetite: -0.3 decrease (r = .60, p < .0001); and fear of aversive consequences: -1.1 decrease (r = .33, p = .05). Linear mixed models revealed significant weekly improvements for each candidate mechanism across the full sample (ps < .0001). There were significant interactions for the sensory and fear of aversive consequences modules-for each, participants who received the corresponding module had significantly larger decreases in the candidate mechanism than those who did not receive the module. DISCUSSION: Sensory sensitivity and fear of aversive consequences improved more if the CBT-AR module was received, but lack of interest/low appetite may improve regardless of receipt of the corresponding module. Future research is needed to test target engagement in CBT-AR with adaptive treatment designs, and to identify valid and sensitive measures of candidate mechanisms. PUBLIC SIGNIFICANCE: The mechanisms through which components of CBT-AR work have yet to be elucidated. We conducted an exploratory investigation to test if assignment (vs. not) to a CBT-AR module resulted in larger improvements in the corresponding prototypic ARFID motivation that the module intended to target. Measures of the sensory sensitivity and the fear of aversive consequences motivations improved more in those who received the corresponding treatment module, whereas the lack of interest/low appetite measure improved regardless of if the corresponding module was received.