"Theory of mind" is Impaired in Huntington's Disease

Background: Huntington's disease (HD) is an autosomal dominant degenerative brain disorder that is characterized by motor, cognitive, and affective symptoms. There is, to some, degree, phenomenological overlap with schizophrenia. Schizophrenia patients are frequently impaired in "theory of mind'' (ToM), that is, the ability to reflect on the mental states of self and others, with mixed evidence for a ToM deficit in HD. Methods: We examined ToM and neurocognitive functioning in 25 patients diagnosed with HD. For comparison, 25 patients with schizophrenia and 25 healthy controls, matched for age and gender, were included. Results: Patients with HD were impaired in ToM relative to controls. The pattern of neurocognitive deficits including ToM strikingly resembled the one found in schizophrenia, suggesting a selectively impaired ToM. In contrast to previous schizophrenia research, ToM was not associated with functional measures on the Unified Huntington's Disease Rating Scale (UHDRS). Conclusions: The present study shows that patients with HD have deficits in ToM similar to schizophrenia. The association of impaired ToM with function needs to be established in future studies using rating scales that more specifically address interpersonal problems. (C) 2011 Movement Disorder Society