A study of psychiatric morbidity in patients with Huntington's disease, their relatives, and controls. Admissions to psychiatric hospitals in Denmark from 1969 to 1991.

Psychiatric morbidity among 74 non-affected first-degree relatives and 93 non-affected second-degree relatives of patients with Huntington's disease (HD) was compared with that of 37 patients with HD and with matched control groups. Due to specific age criteria, the first-degree relatives were at decreased risk and the second-degree relatives at negligible risk of being carriers of the gene for HD. Information on admissions to departments of psychiatry and diagnoses at discharge were obtained for all subjects from a nationwide central register. Psychiatric morbidity was no greater among relatives than among controls, whereas HD patients had significantly more admissions and psychiatric diagnoses than relatives. Growing up with a risk of developing HD does not itself increase the risk of developing psychiatric illness resulting in hospital admission. Severe psychiatric disorders in HD patients were thus most likely to be aetiologically related to the disease process, possibly through a genetic mechanism.