Behavioural tendencies toward food in anorexia nervosa: a mobile approach-avoidance task evaluation

Anorexia nervosa (AN) is a psychiatric disorder which is severe, persistent, and difficult to treat, causing significant impairments in physical, cognitive, and socio-emotional areas. These impairments negatively affect the quality of life and represent the psychiatric disorder that carries one of the worst mortality rates. A distinct feature of the restricting subtype of AN is a rigid, extreme reduction of food intake, which is successfully maintained even in critical situations of malnutrition. Implicit biases in behavioural tendencies, such as approach-avoidance biases towards salient stimuli, were considered a possible explanation for the maintenance of the disease. The aim of this exploratory study was to investigate the existence of an implicit bias towards food in a clinical sample of patients with restrictive AN diagnosis and a healthy control (HC) group. The current work is the first to implement a new mobile approach-avoidance task (AAT) in a restricted AN sample, presenting high-calorie, low-calorie, and neutral object stimuli, with food being a relevant task feature. As predicted, AN patients showed a reduced approach bias for food stimuli compared to the HC group, which conversely expressed a clear approach tendency for food. Furthermore, for both HC and AN groups, approach-avoidance responses were not affected by the calorie content of food stimuli. Therefore, contrary to what was predicted, no greater reduction of the approach bias was observed for high-calorie versus low-calorie food in AN participants. These results improve the understanding of implicit behavioural tendencies that may play a fundamental role in the maintenance of dysfunctional behaviours in AN. This finding may advance clinical interventions for AN by enhancing current psychotherapy approaches with targeted therapies for their cognitive and behavioural biases, as, for instance, AAT training.