Exploring the relationship between proactive inhibition and restrictive eating behaviours in severe and enduring anorexia nervosa (SE-AN).

Background: There is a need for improved understanding of why 20-30% of individuals with anorexia nervosa (AN) develop a severe and enduring form of illness (SE-AN). Previously, we reported differences in proactive inhibition (a pre-emptive slowing of responses) in individuals with AN compared to healthy controls (after controlling for intolerance of uncertainty). The present study is a preliminary exploration of proactive inhibition in which we compared women with SE-AN with healthy comparison (HC) women and explored its association with restrictive/avoidant eating behaviours.

Methods: Thirty-four women with SE-AN (defined by >3 years of illness and a previous unsuccessful course of eating disorder treatment) and 30 HCs completed (a) a cued reaction time task, to assess proactive inhibition, and (b) questionnaires assessing restrictive/avoidant eating behaviours and intolerance of uncertainty.

Results: Both SE-AN and HC participants showed slower reaction times under conditions of uncertainty, indicating proactive inhibition in both groups. There was a main effect of group, with SE-AN participants showing significantly slower reaction times compared to HC. There was no interaction between group and condition, suggesting that individuals with SE-AN did not differ in proactive inhibition compared to HCs. However, post-hoc analysis between-group tests for each trial type revealed that group differences were only present under conditions of uncertainty. Proactive inhibition was not significantly associated with self-reported restrictive/avoidant eating behaviours, including when taking intolerance of uncertainty into consideration.

Conclusions: It is unlikely that proactive inhibition contributes to avoidant and restrictive eating behaviours seen in SE-AN. Our findings suggest that the SE-AN group are relatively more cautious when responding under conditions of uncertainty. Longitudinal studies and between-group comparisons of individuals across different stages of illness will be required to elucidate the way in which proactive inhibition is specifically implicated in SE-AN, rather than in AN more generally.