Numerous studies of the beliefs of people with anorexia nervosa (AN) suggest that a subset of such individuals may experience delusions. We first describe what makes a belief delusional and conclude that such characteristics can be appropriately applied to some beliefs of people with AN. Next, we outline how delusional beliefs may relate to the broader psychopathological process in AN, including: (1) they may be epiphenomenal; (2) they may be an initial partial cause of AN; (3) they may be caused by aspects of AN; or (4) they may be sustaining causes, possibly involved in reciprocal causal relations with aspects of AN. We argue that there is good reason to believe that delusional beliefs of people with AN are not merely epiphenomenal, but rather that they’re causally connected to AN. Because of this, empirical studies can be designed to test for the presence of causal relations. We describe how these studies should be designed. The results of such studies have important implications for understanding the experience of individuals with AN and for the treatment of AN. We outline these implications.
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See Lancellotta and Bortolotti (2019), pp. 9–11 for discussion.
See Radden (2011), Chap. 2: “Varieties of Clinical Delusion”, pp. 17–38, for a nice discussion of delusion features.
See Bortolotti and Miyazono (2015), pp. 637–639.
The argument rests on thinking of beliefs as essentially reason-responsive and action-guiding, but we think that these are not constitutive features of beliefs, but rather rational standards for belief. Additionally, there is ample reason to think that “regular” beliefs often fail to be reason-responsive and action-guiding. See Bentall (2003) and (2018) for good examples of this, as well as Bortolotti et al. (2017).
These aren’t the only ways to distinguish delusions. We might note their negative practical impact (impairments to everyday functioning, psychological harm, compromised social relationships, etc.) or their cause (dysfunctional mental states, brain damage, etc.). But delusions can have differing practical effects, both positive and negative, and it’s difficult to determine their cause. So, we focus on content, fixity, rationality, conviction, and insight, all of which are featured in the DSM and/or BABS.
It’s not clear what is meant by “external reality”. Perhaps it gestures at the fact that the content of many delusions concerns the world external to the agent. This is another way the DSM characterizations focus on belief content to identify delusions. But one could have a delusion about internal reality (e.g. one’s own mental states), so the “external reality” clause isn’t a helpful focus. See also Coltheart et al. for critical discussion of both the focus on inference and the focus on external reality in DSM characterizations of delusion (2011, pp. 275–276).
It’s not necessary to use ‘fixedness’ to describe this feature. We’re not committed to the word. We are committed to the concept we’re trying to associate with the word.
Note that thinking of delusion as partly constituted by fixedness doesn’t automatically count religious and culturally-shared beliefs as delusional, because while fixedness is a necessary condition for delusion, we have not argued that it’s sufficient. In keeping with this, the view also doesn’t automatically count belief in conspiracy theories as delusional. Our view of delusion leaves open the possibility that certain of these beliefs may well be delusional, but we think this is a useful result. A good characterization of delusion should not automatically decide the question of whether certain types of beliefs are delusional.
One might resist the idea that this belief counts as delusional if one also wants to maintain that all delusional beliefs cause some form of impairment, distress, or harm. But we think it’s more useful to count this sort of belief as delusional and address separately whether the belief causes impairment, distress, or harm.
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De Young, K., Rettler, L. Causal Connections Between Anorexia Nervosa and Delusional Beliefs. Rev.Phil.Psych. (2023). https://doi.org/10.1007/s13164-023-00703-y