In the 1871 Census people were asked whether any member of the household was an 'imbecile or idiot' or 'feeble-minded', a question that was retained until the 1911 Census.
The exact definitions of terms such as 'lunatic', 'imbecile', 'idiot' and 'feeble-minded' are extremely problematic. According to the 1881 Census Report;
No accurate line of demarcation can be drawn between the several conditions indicated by these terms. Speaking generally, however, the term idiot is applied in popular usage simply to those who suffer from congenital mental deficiency, and the term imbecile to persons who have fallen in later life into a state of chronic dementia. But it is certain that neither this nor any other definite distinction between the terms was rigorously observed in the schedules, and consequently no attempt has been made by us to separate imbeciles from idiots. The term lunatic also is used with some vagueness, and probably some persons suffering from congenital idiocy, and many more suffering from dementia, were returned under this name.Considering that householders, who could be illiterate, were being asked to give information about medical disabilities without any definition of the terms being used the answers should be treated with caution. Also they would be unwilling to admit that anyone in the family had medical disabilities.
If you want to find out more look at
On the Diagnosis and Prognosis of Idiocy and Imbecility
http://www.personal.dundee.ac.uk/~mksimpso/IreDiag.htmStan
