Skip to main content

Fixity of Delusions

Today's post is by George Chapman, an academic psychiatrist-in-training currently based at the University of Oxford, and Robert Howard, Professor of Old Age Psychiatry at University College London and Honorary Consultant Psychiatrist at the North London NHS Foundation Trust.

         
George Chapman

Robert Howard

Delusions are classically described as ‘fixed’ false beliefs. This description was first articulated by Karl Jaspers and, while it is widely considered to be an overstatement or incomplete, it still forms the basis of definitions found in the Diagnostic Statistical Manual (DSM) and International Classification of Diseases (ICD).

In recent years, there have been tremendous advances towards unravelling why and how delusions emerge. However, much less has been learned about why or how delusions are persistently sustained once formed. This discrepancy motivated our just-published narrative review, “On the fixed nature of delusions” which I briefly summarise here.

We begin by asking what it really means for a delusion to be ‘fixed’. We review existing clinical rating scales that explicitly seek to measure the ‘fixity’ of delusions and other beliefs, and find that ‘fixity’ has been variably understood, defined and applied. We suggest a clearer vocabulary around the fixity of delusions moving forward, in terms of their conviction (subjective certainty in a delusion), incorrigibility (resistance to counter-evidence), persistence (continuous maintenance with mostly unchanged content) and stability (repeated emergence with mostly unchanged content).

Next, we consider how fixed delusions really are. We uncover evidence from the literature that delusions are less strongly fixed than classical descriptions imply. In terms of conviction, as few as two-fifths of patients with schizophrenia spectrum disorders have total certainty in their delusional beliefs. In terms of incorrigibility, as many as one-third of patients with schizophrenia spectrum disorders would be less sure of their delusions if confronted with evidence against them. In terms of persistence, just 15% of patients with delusions at baseline, who were then seen at 10-week intervals for a year, had delusions at every appointment. In terms of stability, only 40-45% of patients with delusions at baseline still had delusions 8 to 39 years later. 

We then explore the determinants of delusion fixity. We include all identifiable articles that have, in some way, considered drivers for and against conviction, incorrigibility, persistence, stability or their equivalents. We find at least 35 factors linked with greater delusion fixity, as well as 2 factors linked with lesser delusion fixity, across diagnostic, psychopathological, psychodynamic, social, cognitive, metacognitive and cognitive neuroscience perspectives. Many of these are incorporated into a new working model of delusion fixity, shown below:



We end by drawing attention to current limitations to thought in the field and suggest some future directions. Of particular importance, existing studies into the determinants of fixity have neglected incorrigibility and stability in relation to conviction and persistence. Moreover, mechanistic studies, particularly those exploring metacognitive and neural mechanisms, as well as the role of antipsychotic medication in patients, are lacking. 

Finally, almost all extant studies are cross-sectional, limiting the fidelity of insights gained, particularly with respect to establishing causality. We therefore advocate for conduct of longitudinal studies in patients taking antipsychotic medication, which should triangulate psychopathology, (meta)cognitive processes and their underlying computations, in the pursuit of an integrated understanding of delusion fixity.


Labels:

Popular posts from this blog

Delusions in the DSM 5

This post is by Lisa Bortolotti. How has the definition of delusions changed in the DSM 5? Here are some first impressions. In the DSM-IV (Glossary) delusions were defined as follows: Delusion. A false belief based on incorrect inference about external reality that is firmly sustained despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not one ordinarily accepted by other members of the person's culture or subculture (e.g., it is not an article of religious faith). When a false belief involves a value judgment, it is regarded as a delusion only when the judgment is so extreme as to defy credibility.
Read more

Motivated Reasoning in Science

Today's post is by Josh May (University of Alabama, Birmingham). In this post, he talks about one of his papers published in Synthese and entitled " Bias in Science ". Josh May Much discussion of the replication crisis in science has focused on the social sciences, particularly psychology. A common narrative is that the social sciences are particularly susceptible to powerful biases, such as moral and political ideology. I argue instead for a parity thesis: all areas of science are subject to bias, through the general psychological mechanism of motivated reasoning . This provides a unified framework for understanding how values influence the entire scientific enterprise. The scientific process involves numerous decisions that can be influenced by one's values--including moral, political, and prudential values--which manifest as goals or motivations. A researcher wants badly, say, to publish in a prestigious journal in order to either advance her career or maintain ...
Read more

Rationalization: Why your intelligence, vigilance and expertise probably don't protect you

Today's post is by Jonathan Ellis , Associate Professor of Philosophy and Director of the Center for Public Philosophy at the University of California, Santa Cruz, and Eric Schwitzgebel , Professor of Philosophy at the University of California, Riverside. This is the first in a two-part contribution on their paper "Rationalization in Moral and Philosophical thought" in Moral Inferences , eds. J. F. Bonnefon and B. Trémolière (Psychology Press, 2017). We’ve all been there. You’re arguing with someone – about politics, or a policy at work, or about whose turn it is to do the dishes – and they keep finding all kinds of self-serving justifications for their view. When one of their arguments is defeated, rather than rethinking their position they just leap to another argument, then maybe another. They’re rationalizing –coming up with convenient defenses for what they want to believe, rather than responding even-handedly to the points you're making. Yo...
Read more