Hypnotic illusions and clinical delusions: Hypnosis as a research method

Introduction. Hypnosis is not only intrinsically interesting, but it can be used instrumentally as a powerful tool to investigate phenomena outside its immediate domain. In focusing on instrumental hypnosis research, we first sketch the many contributions of hypnosis across a range of areas in experimental psychopathology. In particular, we summarise the historical and more recent uses of hypnosis to create and explore clinically relevant, temporary delusions. Methods. We then describe in detail the steps that hypnosis researchers take in constructing a hypnotic paradigm to map the features and processes shared by clinical and hypnotic delusions, as well as their impact on information processing (including autobiographical memory). We illustrate with hypnotic versions of mirrored-self misidentification, somatoparaphrenia, alien control, and identity delusions. Results. Findings indicate that hypnotic analogues can produce compelling delusions with features that are strikingly similar to their clinical counterparts. These similarities encompass phenomenological features of delusions, delusional resistance to challenge, and autobiographical memory during delusions. Conclusion. We recognise important methodological issues and limitations of such hypnotic analogues, including: indexing response (behaviour vs. experience), alternative explanations (e. g., social compliance), the need for converging data, the need for close and continuing dialogue between the clinic and the laboratory, and generalisability of the findings.