Descriptive Psychopathology: The Signs and Symptoms of ...

287 Chapter 11: Delusions and abnormal thought contentwhite horse?” the patient with Ganser’s syndrome might immediately and withconviction respond “Brown”.Folie à deux (folie communiquée, folie imposée, folie induite,shared delusional disorder)The French neurologists Ernest-Charles Lasegue and Jean Pierre Falret in 1877first described a phenomenon of “psychological contagion” as mutually inducedfalse ideas formed by two or more people. 60 William Hammond refers to thephenomenon as La folie simultanée, restricted to two or more members of thesame family becoming ill at the same time, and not a psychological phenomenon. 61Case literature finds males and females equally affected, with the duos comprised ofmarried couples, siblings (often monozygotic twins), and mother–child dyads.Common co-conditions are dementia, depressive illness and mental retardation. 62Although the occurrence is commonly in isolated dyads with one member saidto be dominant and the other submissive and suggestible, the conditions reportedas folie à deux typically have substantial heritability. Assortative mating in coupleswith mental illness is also well documented, and these factors may account forco-delusions. 63 In one report both parties to a Doppelganger delusion had evidenceof cerebral dysfunction. 64Over-valued ideasOver-valued ideas are beliefs that are plausible, may contain a “kernel of truth”,and may be accepted by others. The ideas, however, intrude into the foregroundof thought at the expense of other considerations. The sufferer pursues the ideadespite the quest leading to interpersonal and financial difficulties, and does notperceive the idea as unusual (conceded by some delusional patients), or asincorrect (understood by obsessional patients). Once established, over-valuedideas persist indefinitely.The source of over-valued ideas was classically considered a remembrance of anemotional experience, but there is no evidence for this interpretation. Patientswith over-valued ideas, however, have strong emotions about them. Eugen Bleulerconsidered them to be exaggerations of personality traits that could becomedelusional. In such instances, monomania was diagnosed. 65Obsessions (or compulsive notions) and ruminations 66Obsessions are ideas which continually intrude into the patient’s thinking withor without external stimulation. The content is often recognized by the patientas incorrect, except in states of intense emotion. The thoughts are perceived