Supplementary Material for: Towards a Multi-Level Phenomenology of Delusional Disorder: The Dissociative Thought-Script

Delusional disorder (DD) is still considered a diagnosis of exclusion for a difficult-to-treat condition characterised by the presence of delusional beliefs in the absence of other psychiatric symptoms. Attempts to contextualise psychological processes recognised since the earliest observations of this disorder have had very limited impact on improving some fixed beliefs. In the Cambridge Early Intervention in Psychosis Service we have observed a particular phenomenon, often categorised as a delusional idea in the context of DD, which manifests through highly repetitive belief expression that fails to respond to pharmacological and psychological treatments. Key aspects of this phenomenon are similar to those observed in dissociative (functional neurological) presentations. Drawing on the Integrative Cognitive Model of functional neurological disorders, we developed a successful psychological intervention that places less emphasis on challenging delusional content and focuses more on dismantling dissociation and underlying affective factors associated with the activation of the fixed belief. Our initial findings reinforce the need to continue developing a multi-level phenomenological approach to define a variety of symptoms traditionally grouped under the concept of “delusion.