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A recent news article in @ScienceMagazine, “Rethinking #anorexia: Biology may be more important than culture,” illustrates the human tendency to stay committed to a simple theory despite contrary evidence, even when this slows research progress.
https://www.sciencemag.org/news/2020/04/rethinking-anorexia-biology-may-be-more-important-culture-new-studies-reveal 1/10
https://www.sciencemag.org/news/2020/04/rethinking-anorexia-biology-may-be-more-important-culture-new-studies-reveal 1/10
The article cites evidence for genetic factors that influence the risk of #anorexia to argue that it is a “biological” disorder, not a psychological one. This false dichotomy persists in part because of misinterpretation of genetic findings such as… 2/10
A 2019 meta-analysis of 33 datasets with 16,992 cases of anorexia nervosa and 55,525 controls identified 8 statistically significant loci. The 100+ authors concluded “that these genes may have a role in the etiology of anorexia nervosa.” Not really.
https://www.nature.com/articles/s41588-019-0439-2 3/10
https://www.nature.com/articles/s41588-019-0439-2 3/10
The polygenic risk score accounted for only 1.7% of variation. But the bigger problem is the assertion that genetic influences make a condition a biological disease. A tendency to vote Republican is also heritable, but it is not a genetic disease. https://journals.sagepub.com/doi/abs/10.1177/1065912917698045 4/10
An anorexia researcher discounts the role of socio-cultural factors by observing that “Exposure to this ideal [of thinness] is ubiquitous, but everybody doesn’t get anorexia nervosa.” That is like arguing that smoking does not cause cancer because not all smokers get sick. 5/10
Patients who report being unconcerned about thinness are cited as evidence that anorexia may have a primary genetic or brain cause. As a consultation psychiatrist, I have seen cases of anorexia caused by a hypothalamic tumor, cancer or metabolic disease, but they are rare. 6/10
Most eating disorders start with restrictive dieting. My clinical experience matches Hilbert’s 2014 finding that “Dieting was the most common onset symptom in AN.” https://www.sciencedirect.com/science/article/pii/S0165178114004740 7/10
The influence of social factors does not makes anorexia “psychological,” nor does it imply that it is voluntary or the fault of the patient or the parents. Atherosclerosis is more common in cultures with fast food, but that does not make heart disease psychological. 8/10
The idea that anorexia is caused by primary genetic or brain causes was worth pursuing, but contrary evidence should broaden the search, not motivate greater commitment to a simplistic schema. What has been missing is an understanding of evolved eating regulation mechanisms. 9/10
Famine protection mechanisms shaped by natural selection are vulnerable to dysregulation. Severe dietary restriction induces uncontrollable eating, causing more fear of obesity and greater efforts to diet that cause more binging in a vicious positive feedback cycle. 10/10
Most people stop dieting, some persist in bulimia, a few slip into the behavioral trap of anorexia nervosa. It is a real biological disease. Who succumbs can’t be predicted by social factors any better than genetics, but restrictive dieting is usually central to causation. 11/11
It is time to stop assuming that genes or brain abnormalities cause anorexia, and to start investigating how evolved eating regulation mechanisms interact with social factors to cause this devastating deadly disease. 12/12
http://goodreasons.info
http://goodreasons.info
