I was completely convinced I was God. I needed to go out and bless via libraries (Isham et al., 2019).
It just felt like you’re being watched and perhaps people are following your every moves, so you have to be careful (Bögle & Boden, 2019).
Believing you are God, that you are under surveillance by MI5, or that aliens are targeting you. These may seem like extraordinary or impossible experiences, but for those who experience them, these beliefs feel entirely real. These are examples of delusional beliefs; a false, fixed belief that is strongly held despite evidence that it is not true and is not ordinarily held by others in the same socio-cultural group. Delusions emerge in a variety of disorders and can have negative effects on day-to-day functioning (McKay et al., 2005), and psychological well-being (Freeman, 2014).
Delusional beliefs often follow similar patterns, and they can be grouped into themes. For example, one of the most common themes is known as persecutory delusions. These are beliefs where someone is intending to cause you harm. Some of the measures used to assess delusional beliefs include more themes than others. However, studies often include reports of delusion themes that don’t appear in any manuals or scales, especially when reporting themes across different cultures. So, which ones are important to classify?
A previous meta-analysis (Collin et al., 2023) looked at only five themes. Therefore, Pappa et al. (2025) set out to fill a gap in the literature and offer the most comprehensive meta-analysis of delusional themes to date.
This new review sought to widen the lens on delusional beliefs.
Methods
To find studies that reported delusional theme prevalence, the authors searched five databases using a variety of search terms and reviewed the references of identified papers. Each study was independently screened by two out of the three authors, and a fourth author judged any disagreements using a standardised platform. Studies eligible for inclusion had to meet the following criteria:
- Trial and observational studies
- Mean age of 18-65
- Published in English
- Reported the prevalence of delusional theme cases per sample measured by a mental health professional.
The authors excluded literature reviews, case studies, and opinion articles. 4,545 studies were identified, and 155 reports met the final criteria.
Pappa et al (2025) ran two multivariate multilevel random-effects meta-analyses. In other words, they ran two tests, which combined results from all the studies while accounting for the fact that some studies reported multiple samples and others reported multiple delusional themes within each sample. One meta-analysis looked at delusional themes from established assessment scales, and the other also included data from ad hoc and clinical assessments.
They also examined associations between delusional themes and a range of clinical, demographic and study characteristics such as mean age, diagnosis, and GLOBE cultural dimension classification.
Results
In the meta-analysis 21 themes were identified. The 10 most common were:
- Persecutory/ paranoid
- Reference
- Grandiose
- Schneiderian
- Religious
- Control
- Mindreading
- Sexual
- Thought broadcast
- Bizarre
In the analysis, which included all assessments, 37 delusional themes were identified. The 10 most common were:
- Persecutory/ paranoid
- Reference
- Family/ relatives
- Grandiose
- Passivity
- Schneiderian
- Neighbours/ friends/ associates
- Spied on or watched
- Paranormal
- Sexual
When analysing delusional themes from assessment scales only, the only association identified in the meta-regression analysis showed that in studies with a higher percentage of female patients, there were more guilt/sin delusions. This association was not found when the authors included structured and unstructured assessments. Unlike in the initial analysis, the more inclusive analysis found associations between GLOBE cultural clusters and some delusional themes:
- Southern Asia (India, Indonesia, Iran, Malaysia, Philippines, Thailand): increased jealousy delusions
- Eastern Europe (Albania, Georgia, Greece, Hungary, Kazakhstan, Poland, Russia, Slovenia): increased guilt/sin delusions
- Middle East (Egypt, Kuwait, Morocco, Qatar, Turkey): increased sexual and jealousy delusions
- Confucian Asia (China, Hong Kong, Japan, Singapore, South Korea, Taiwan): increased persecutory/paranoid and delusional perception
The authors also looked at how much more or less common delusional themes are in a variety of mental health diagnoses compared to the broad category of psychosis. There were many associations found in the meta-analysis that only included themes from established assessment scales. For example, mood disorders were associated with an increased prevalence of grandiose, guilt/sin, sexual, religious, and primary delusions. When including data from ad hoc and clinical assessments, this association was not found. In this analysis, they found some associations between diagnosis and delusional themes that were consistent with the first:
- First episode psychosis was associated with increased prevalence of reference and persecutory/ paranoid delusions.
- Delusional disorder was associated with an increased prevalence of jealousy and a decreased prevalence of grandiose delusions.
In studies that did not rely solely on assessment scales, delusions were more commonly about people socially closer, such as family, versus people who are socially distant, such as neighbours. The analysis also revealed that there aren’t any delusional themes classified in assessment scales that focus on the type of individual. This could be an important factor in predicting risk.
The authors ran sensitivity analyses to see which studies might influence the results of the meta-analysis and found that removing these studies made no substantial difference to the results.
In both analyses persecutory/paranoid beliefs were the most common grouping.
Conclusions
The authors concluded:
Many commonly reported themes are not included in standard classifications. Relationship to culture was modest but more present when not relying solely on established scales.
In line with existing literature, the meta-analysis showed that persecutory and paranoid delusions are the most common among patients with psychosis. However, Pappa et al. (2025) identified more themes than those currently represented in assessment tools, suggesting that they underrepresent clinically relevant delusional content.
The authors found very few differences in the prevalence of delusional themes between GLOBE cultural clusters. This could mean that most themes are stable across social environments, which suggests that they may be common cognitive mechanisms in social interactions across cultures. However, this method of classification has many limitations, and more research is needed to understand delusional themes across different cultures.
The landscape of delusional themes is much more diverse than diagnostic manuals and assessment scales account for.
Strengths and limitations
Strengths
- Comprehensive sample. The study drew on 155 studies from 37 countries, incorporating both structured assessment data and ad hoc clinical observations, making it more representative of global psychosis presentations.
- Robust methodology. The use of a multivariate, multilevel meta-analysis allowed the authors to account for multiple themes and multiple samples within the same study, reducing statistical bias and producing more robust estimates.
- No evidence of publication bias. There was no evidence of selective reporting of statistically significant studies, increasing the reliability and validity of the results.
- Moderate within-study heterogeneity and low between-study heterogeneity. There was some variability between patients within the studies, but the findings were fairly consistent across the different studies.
Limitations
- The authors used the GLOBE cultural clusters to define culture. This is a limited method as it oversimplifies and generalises cultures without considering differences within clusters.
- The review was limited to studies published in English. This means that the results are likely to under-represent findings from non-English-speaking countries and bias cultural comparisons. As a result, the conclusions drawn may be biased toward English-speaking populations and may not fully capture cultural variations. This is a particularly notable limitation of the study, given poor understanding of cultural variation in delusions was a theoretical driver.
- Assessment scale cut-off points may differ. If different tools use different thresholds, someone might meet the criteria according to one scale but not according to another, making it difficult to investigate the true prevalence of delusional themes. As the thresholds were not commonly reported, the authors could not analyse how this might have affected the results.
- Exclusion of case studies and opinion articles. This would likely exclude first-person accounts of living with psychosis and associated delusions. While including them may have made the systematic review and meta-analysis too difficult to carry out, first-person accounts would be extremely valuable in providing insights into delusional beliefs and may offer a broader understanding of delusional themes and cultural contexts.
Implications for practice
This new evidence by Pappa et al. (2025) reveals that the landscape of delusional themes is much more diverse than diagnostic manuals and assessment scales account for. A deepened understanding of the prevalence of delusional themes is important and can be used to inform clinical decisions, help assess risk, and target interventions.
There were many themes discovered that do not appear in any of the assessment scales reported in this study. This means that clinical assessment may be missing key information that could help inform formulation and treatment. Clinicians need to be aware that scales and measures are not exhaustive and may fail to accurately capture the full breadth of delusional experiences of service users. They should remain attentive to ‘non-classical’ delusions to effectively assess, formulate, and plan patients’ care.
While the methods used to classify culture were limited, the current analysis shows some interactions between culture and delusional themes. Therefore, clinicians need to be attuned to cultural influences on the content and expression of delusional beliefs. More research is needed to understand these cultural influences.
This meta-analysis has offered some important suggestions for avenues that can be explored in future research. The range of delusional themes captured reveals many areas where more research is needed to develop reliable assessment tools and guide the development of targeted interventions and treatments. Recent literature has investigated the cognitive mechanisms that underlie these delusional themes and demonstrated that they can serve as meaningful targets for intervention. For example, themes that focus on the type of individual might be a valuable area for research. In addition, research that includes a broader range of evidence, including first-person narratives, is needed to enrich our understanding of delusional beliefs.
Beyond identifying types of delusional themes and how common they are among people with psychosis, some of the studies in the analysis also reported other characteristics of delusions, including the degree of preoccupation with the belief, the level of distress caused, and whether any of the delusional themes are related to one another. Considering other perspectives and dimensions of delusional beliefs will provide a more comprehensive understanding of the severity, impact and complexity of delusions.
Overall, the wider understanding of delusional themes that this paper offers highlights important implications for mental health practice and highlights many areas for further research.
The scales we use to assess and measure delusions may be inadequate.
Links
Primary paper
Pappa, E. et al. (2025) ‘Delusional themes are more varied than previously assumed: A comprehensive systematic review and meta-analysis’, Schizophrenia Bulletin, 51(3), pp. 637–645.
Other references
Bögle, S. and Boden, Z. (2019) ‘‘It was like a lightning bolt hitting my world”: Feeling shattered in a first crisis in psychosis, Qualitative Research in Psychology, 19(2), pp. 377–404.
Collin, S. et al. (2023) Delusions and the dilemmas of life: A systematic review and meta-analyses of the global literature on the prevalence of delusional themes in clinical groups, Clinical Psychology Review, 104, p. 102303.
Freeman, D. et al. (2013) Persecutory delusions and psychological well-being, Social Psychiatry and Psychiatric Epidemiology, 49(7), pp. 1045–1050.
Isham, L. et al. (2019) Understanding, treating, and renaming grandiose delusions: A qualitative study, Psychology and Psychotherapy: Theory, Research and Practice, 94(1), pp. 119–140. doi:10.1111/papt.12260.
McKay, R., Langdon, R., & Coltheart, M. (2005). “Sleights of mind”: Delusions, defences, and self-deception. Cognitive Neuropsychiatry, 10(4), 305–326.