Are clinical delusions adaptive?

A Bayesian predictive processing account of Othello syndrome in Parkinson's disease

Introduction: Although delusions in Parkinson's disease (PD) are rare, when they occur they frequently take the form of "Othello syndrome": the irrational belief that a spouse or partner is being unfaithful. Hitherto dismissed as either a by-product of dopamine therapy or cognitive impairment, there are still no convincing theoretical accounts to explain why only some patients fall prey to this delusion, or why it persists despite clear disconfirmatory evidence.Methods: We discuss the limitations of existing explanations of this delusion, namely hyperdopaminergia-induced anomalous perceptual experiences and cognitive impairment, before describing how Bayesian predictive processing accounts can provide a more comprehensive explanation by foregrounding the importance of prior experience and its impact upon computation of probability. We illustrate this new conceptualisation with three case vignettes.Results: We suggest that in those with prior experience of romantic betrayal, hyperdominergic-induced aberrant prediction errors enable anomalous perceptual experiences to accrue greater prominence, which is then maintained through Bayes-optimal inferencing to confirm cognitive distortions, eliciting and shaping this dangerous delusion.Conclusions: We propose the first comprehensive mechanistic account of Othello syndrome in PD and discuss implications for clinical interventions.

Subjective experience and meaning of delusions in psychosis: a systematic review and qualitative evidence synthesis

BACKGROUND

Delusions are a common transdiagnostic feature of psychotic disorders, and their treatment remains suboptimal. Despite the pressing need to better understand the nature, meaning, and course of these symptoms, research into the lived experience of delusional phenomena in psychosis is scarce. Thus, we aimed to explore the lived experience and subjective apprehension of delusions in help-seeking individuals with psychosis, regardless of diagnosis and thematic content of the delusion.

METHODS

In our systematic review and qualitative evidence synthesis, we searched MEDLINE, Embase, PsycINFO, CINAHL, and Web of Science for qualitative studies published in English from database inception, with the last search on Sept 9, 2021. Grey literature search and hand-searching of relevant journals were also done. Studies were eligible if they provided an analysis of lived experience of delusions or predelusional phenomena presented from the perspective of individuals (age 14-65 years) who had developed a clinical high-risk stage of psychosis, or a diagnosable affective or non-affective psychotic disorder (as clinically defined, self-reported, or assessed within the primary study). Studies with only a subset of relevant participants were eligible only if data for the population of interest were reported separately. Studies that did not discriminate between the experience of delusion and other positive symptoms (eg, hallucinations) were included only if data for delusions were reported separately or could be extracted. First-person accounts (and author interpretations) discussing changes in the sense of self, lived world, and meaning in relation to delusions were extracted and synthesised using a novel thematic synthesis approach informed by a critical realist stance and a phenomenological theoretical framework. Analytic themes were developed into a new overarching framework for understanding the emergence of delusional phenomena. The study was registered with PROSPERO, CRD42020222104.

FINDINGS

Of the 3265 records screened, 2115 were identified after duplicate removal. Of these, 1982 were excluded after title and abstract screening and 106 after full-text eligibility assessment. Of the 27 studies entering quality assessment, 24 eligible studies were included in the qualitative evidence synthesis, representing the perspectives of 373 help-seeking individuals with lived experience of delusions in the context of psychosis. Gender was reported as male (n=210), female (n=110), transgender (n=1), or not reported (n=52). Only 13 studies reported ethnicity, with White being predominant. The age of most participants ranged from 15 to 65 years. We found no eligible studies investigating subclinical or predelusional experiences in at-risk mental state populations through qualitative methods. Most studies were undertaken in western, educated, industrialised, rich, and democratic (WEIRD) societies, and most included participants had received or self-reported a diagnosis within the schizophrenia spectrum. Studies differed in relation to whether they focused on one kind or theme of delusion or delusional phenomena more generally as a unified category. Three superordinate themes relating to experiential changes and meanings in delusion were identified: (1) a radical rearrangement of the lived world dominated by intense emotions; (2) doubting, losing, and finding oneself again within delusional realities; and (3) searching for meaning, belonging, and coherence beyond mere dysfunction. Based on the review findings and thematic synthesis, we propose the Emergence Model of Delusion to advance understanding of delusional phenomena in psychosis.

INTERPRETATION

Delusions are best understood as strongly individualised and inherently complex phenomena emerging from a dynamic interplay between interdependent subpersonal, personal, interpersonal, and sociocultural processes. Integrative approaches to research on delusion, which consider their potential adaptiveness and favour explanatory pluralism, might be advantageous. Effective clinical care for individuals with psychosis might need adapting to match more closely, and take account of, the subjective experience and meaning of delusions as they are lived through, which might also help redress power imbalances and enduring epistemic injustices in mental health.

FUNDING

Priestley Scholars, Wellcome Trust.

Differences between delusional disorder and schizophrenia: A mini narrative review

Psychotic syndromes are divided into affective and non-affective forms. Even among the non-affective forms, substantial differences exist. The aim of this relatively brief review is to synthesize what is known about the differences between two non-affective psychoses, schizophrenia and delusional disorder (DD), with respect to clinical, epidemiological, sociodemographic, and treatment response characteristics. A PubMed literature search revealed the following: in schizophrenia, hallucinations, negative symptoms and cognitive symptoms are prominent. They are rare in DD. Compared to schizophrenia patients, individuals with DD maintain relatively good function, and their delusions are believable; many are beliefs that are widely held in the general population. Treatments are generally similar in these two forms of psychosis, with the exception that antidepressants are used more frequently in DD and, for acute treatment, effective antipsychotic doses are lower in DD than in schizophrenia. It is with the hope that the contrasts between these two conditions will aid in the provision of safe and effective treatment for both that this review has been conducted.

[Psychopathology and Theory of Perceptual Disturbances]

Current classification systems for psychiatric disorders are primarly based on categorial typologies and describe these as distinct nosological entities. A dimensional perspective allows descriptions of a gradual transition between pathologies as well as between normality and pathologies of psychiatric symptoms. Using acoustic hallucinations as most common form of perception disturbances as example, psychiatric-psychopathological and theoretical pros and cons for a dimensional classification of psychiatric symptomatology are sketched in this article. Although doubts concerning the similarity of real perceptions and acoustic hallucinations which underlie such mental events are controversially discussed, many hints could be found for a continuum of hallucinatoric symptoms from the mentally healthy population up to the group of patients with schizophrenia. Studies which investigate the neurophysiological mechanisms of acoustic hallucinations such as hearing voices in healthy persons in comparison to those in patients with schizophrenia could contribute to further differentiation.

Are clinical delusions adaptive?

Delusions are symptoms of psychiatric disorders such as schizophrenia and dementia. By and large, delusions are characterized by their behavioral manifestations and defined as irrational beliefs that compromise good functioning. In this overview paper, we ask whether delusions can be adaptive notwithstanding their negative features. Can they be a response to a crisis rather than the source of the crisis? Can they be the beginning of a solution rather than the problem? Some of the psychological, psychiatric, and philosophical literature has recently suggested that they can. We consider different types of delusions and different ways in which they can be considered as adaptive: psychologically (e.g., by increasing wellbeing, purpose in life, intrapsychic coherence, or good functioning) and biologically (e.g., by enhancing genetic fitness). Although further research is needed to map the costs and benefits of adopting and maintaining delusional beliefs, a more nuanced picture of the role of delusions in people's lives has started to emerge.

This article is categorized under:

Philosophy > Representation

Philosophy > Knowledge and Belief

Neuroscience > Cognition