Changing habits in anorexia nervosa – a randomized controlled trial (CHAiN)

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Anorexia Nervosa (AN) is a serious mental disorder that is mainly characterized by severe restriction of food intake, resulting in underweight. AN affects up to 4% of women during their lifetime, a chronic course with severe somatic sequelae is common, and the mortality rate is the highest of any mental disorder. Irrespective of the treatment approach, recovery rates are low to moderate, whereas attrition and relapse rates are high. One reason for the unsatisfactory effectiveness of available treatments is that still relatively little is known about the etiology and maintenance of the disorder. However, recently, a neurobiologically informed, mechanistic model of AN has been developed which suggests that much of the problematic behaviors in AN (e.g. dietary restraint, counting calories, body checking, excessive exercising) are habitual, meaning that these have shifted from goal-directed to rigid, cue-elicited, automatic behaviors that have been uncoupled from positive or negative consequences. In line with his, neuroimaging research has shown that patients with AN show increased brain activity in the dorsal striatum (a brain region that mediates habitual behavior) during food-related decision-making. Joanna Steinglass, a collaborator on the proposed research project, has recently translated these findings into a novel psychological intervention that specifically targets eating-related habits in AN (REaCH). In a small randomized controlled proof-of-concept study (n=22), this intervention outperformed an active control group (supportive psychotherapy) in terms of reductions in eating-related habit strength (d=1.28) and self-reported eating disorder psychopathology (d=0.81), and increased caloric intake in a laboratory meal (d=1.16). Based on these promising preliminary findings, the central research question of the proposed research project is whether this specific intervention definitely changes the proposed mechanisms and leads to improved clinical results. The planned study is a mono-center randomized controlled superiority trial in n=110 patients with AN, comparing two parallel treatment arms as adjunct to inpatient treatment as usual. The primary outcome will be change in body mass index (BMI), measured at baseline, during each week of the intervention (4 weeks), at the end of treatment and at 6 months follow-up. Secondary outcomes comprise further clinical parameters (self-reported eating disorder psychopathology), surrogate measures (food choices and caloric intake in a laboratory meal), and changes in the mechanism(s) that are targeted by the intervention (eating-related habit strength). The proposed study will provide important results with both direct clinical implications and relevance for an improved understanding of the etiology and maintenance of AN.