The innovative use of hypnosis to study delusions

Since the CCD began, our symptom-focussed research aimed to develop cognitive and neural models of delusions and was guided by the ‘two-factor’ approach developed by Associate Professor Robyn Langdon, Emeritus Professor Max Coltheart and colleagues. According to this approach, two distinct questions need to be answered in order to explain any delusion. First, why does a delusional person generate an implausible belief content in the first place? Second, why does a delusional person fail to revise their belief in response to counter-evidence and rational counter-argument? Testing this theory by studying clinical delusions in the laboratory is difficult. To meet this challenge, we pioneered the use of hypnosis to create temporary, hypnotic analogues of different delusions (Barnier, Cox, Connors, Langdon & Coltheart, 2011). One study that represents the culmination of this line of research drew upon a decade of theoretical and clinical work on the neuropsychology of delusions and combined different methods, and research expertise in a strong cross-disciplinary team (Coltheart, et al., 2018). Our team used non-invasive brain stimulation methods to identify a region of the right frontal cortex that is critical for belief evaluation, which is temporarily disrupted during the hypnotic state and more permanently damaged in clinical delusional cases.