Induced hallucinatory psychosis (folie à deux hallucinatoire): pathogenesis and nosological position

A rare case of a folie a deux in a married couple is presented. The inducing partner (IND) suffered from paranoid hallucinatory psychosis and induced similar symptomatology in his wife. Different from most cases reported in the literature, the induced partner (recipient, REC) also experienced auditory hallucinations (commenting and conversing voices). While the IND recovered fully with a combination of psychotherapeutic as well as neuroleptic treatment, the REC was cured by the psychotherapeutic intervention and the recovery of the IND alone. According to the criteria of current diagnostic systems (DSM, ICD), both patients should have been classified as schizophrenic, due to the presence of the described auditory hallucinations. We conclude that the presence of hallucinations is less specific for a certain diagnosis than implied by such categorical systems and should be regarded as nosologically non-specific symptoms. Modern neurocomputational models of psychopathology, dimensional approaches in the description of hallucinations, as the findings of new functional brain imaging studies support this view. We propose a multidimensional diagnostic process of hallucinations and to classify cases such as the one presented as 'induced hallucinatory psychosis' or 'folie a deux hallucinatoire'.