Wednesday 21 February 2024

Anorexia Nervosa and Delusions – What Can We Learn?

Today’s post is from Kyle De Young and Lindsay Rettler on their recent paper, “Causal Connections between Anorexia Nervosa and Delusional Beliefs” (published in Review of Psychology and Philosophy in 2023). 

Kyle is a clinical psychologist specializing in eating and related behaviors, who oversees the Eating Behaviors Research Lab at the University of Wyoming. Lindsay is a philosopher at UW teaching ethics and philosophy of mental health, who oversees the ethics curriculum for Wyoming’s med school (Wyoming WWAMI Medical Education Program).


Lindsay and Kyle


Anorexia nervosa (AN) is a severe mental disorder associated with mortality and functional impairment. It is complex, multi-systemic (e.g., behavioral, cognitive, endocrine, gastrointestinal), and requires multidisciplinary evidence-based treatment at various levels (e.g., outpatient, inpatient). Despite the availability and use of intense treatments, outcomes are poor, with only 1 in 3 individuals recovering within 9 years. 

Complicating matters is that although 10-30% of individuals with AN experience delusions, AN is not understood as a psychotic disorder nor conceptualized in terms of how delusions relate to its development or maintenance. Focusing on the connections between delusions and AN is a promising way to shed light on this complicated condition, possibly pointing researchers and clinicians in fruitful directions to improve outcomes for this terrible disorder.

Believing that eating a piece of chocolate will cause me to gain 5 lbs might not seem very similar to a psychotic delusion of persecution. But I may hold the belief in a way that floats free of evidence. Is the belief then delusional? The DSM-5 characterizes delusions in varied and sometimes inconsistent ways. These definitions focus on the content of delusions (are they false, unshared, bizarre, etc.?), the degree of conviction with which the delusional belief is held, whether a person has insight to the origins of their belief, whether the belief is irrational, and whether the belief is fixed. 

In our paper we sort through these characterizations and argue that fixedness is the core feature of delusions. When a belief is maintained in a way that’s insensitive to evidence or unresponsive to reasons, the belief is fixed. 

How are these delusions related to AN? We consider several possibilities and conclude that most likely the psychopathology of AN causes delusions, and delusions are likely reciprocally causal with AN. The content of delusions in AN is typically limited to eating, digestion, and body shape/weight, and the delusions function as explanations for behaviors that are otherwise hard to justify. 

Starving oneself to the point of emaciation, medical complications, and interpersonal and occupational impairment when food is readily available are hard to understand without the accompanying delusional belief that one’s body cannot process food, for instance. Delusions may help explain this extreme behavior and in so doing help subdue the fear brought about by AN. As the seriousness of the condition amplifies, the need to hold firmly to the delusion grows.

If delusions and AN are reciprocally causal, intervening on one should improve the other. Most promising is to add treatment components known for their efficacy in ameliorating delusions to existing evidence-based approaches for AN to test whether such additions improve outcomes. Antipsychotic medications that might increase cognitive flexibility could be tried. Some have been tested in AN, generally with underwhelming results, but no trials investigated whether individuals with delusions specifically benefit.

Other approaches include acceptance-based psychotherapies that help individuals change behavior despite their cognitions or specific variants of cognitive therapy developed for delusions. Although we can't estimate the impact on AN of intervening on delusions, even if it helps in only 10-30% of cases, the potential for improving outcomes is great. So, we hope that research will move in this direction!