A third of patients with psychosis remain convinced they are Jesus, a prophet, or a secret genius even after standard treatment—and 78% of them have been physically harmed, sexually exploited, or severely distressed by their own beliefs in the past six months. Current therapies largely ignore grandiose delusions, focusing instead on paranoia or hallucinations. This leaves a gap: no psychological treatment exists that directly targets why people cling to these beliefs—the sense of purpose they provide, the pleasurable rumination that strengthens them, and the acting-out behaviours that confirm them. If this therapy works, it could become the first targeted psychological intervention for harmful grandiose delusions. A successful pilot trial would provide the data needed to launch a definitive randomised controlled trial. That could eventually give clinicians a practical tool to reduce real harm—physical injury, sexual exploitation, emotional collapse—in a patient group that current services are failing.
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Interviewer: 'Could you tell me about your experience of being Jesus?' Kit: 'Well, first off, it's ten years of being sad.' Harmful grandiose delusions Grandiose delusions are when a person is convinced that they have special talents, abilities, mission, or identity when they do not. 34% of patients diagnosed with psychosis (e.g. schizophrenia, schizoaffective disorder, bipolar disorder) continue to present with grandiose delusions despite treatment from mental health services. 78% of these patients report harm being caused over the previous six months by their beliefs. This includes physical harm, sexual harm, and significant emotional distress. Research question Can a theory driven psychological treatment for harmful grandiose delusions be developed that is feasible to deliver, acceptable to patients, and likely to have large clinical benefits? Work to date In an NIHR doctoral fellowship, a new psychological model of grandiose delusions was developed. This was based on a qualitative study with 15 patients with grandiose delusions and quantitative testing with 798 patients with psychosis and 13,000 non-clinical adults. This work identified three key drivers of grandiose delusions: 1. The belief provides a major sense of purpose and meaning in the person's life which is a key motivation for belief retention; 2. Repetitive - often pleasurable - thinking about the delusion brings the belief to mind, elaborates the content, and increases the degree of conviction with which it is held; 3. Immersion behaviours - acting in accordance with the delusional identity - provides compelling evidence for the belief. These mechanisms can be targeted in a psychological therapy to reduce harmful grandiose delusions. Aim To develop and conduct preliminary testing of the first targeted psychological therapy specifically for harmful grandiose delusions. Methods Work-package 1: Therapy development (0-6 months) The therapy will be designed to target the key drivers of grandiose delusions. There will be workshops across the country with patients with lived experience of grandiose delusions. A therapy manual, including patient resources, will be developed, alongside a therapy adherence measure. Work-package 2: Proof-of-concept testing (7-22 months) The therapy will initially be tested with 12 patients using a multiple-baseline across-participant single-case experimental design with randomised baseline length. This will provide initial data on acceptability, satisfaction, and changes in mechanisms and outcomes. The target is a large pre- to post- treatment effect size reduction in grandiose delusions. Work-package 3: A pilot randomised controlled trial (RCT) (23-60 months) An RCT will be conducted with 50 patients to provide further acceptability and satisfaction data, better treatment effect estimation, and additional information needed to inform a definitive RCT. Work-package 4: Inclusivity strategy (0-60 months) Workshops with individuals from Black-African and Black-Caribbean communities will inform the therapy development, and a qualitative study with multi-perspectival design as part of the pilot RCT will facilitate understanding of how individuals from under-served groups experience the therapy. Anticipated impact This research will produce the first targeted psychological intervention for harmful grandiose delusions. By the end of the fellowship there will be all the information required for a grant application to conduct a definitive trial.
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