Disease pattern among 942 mentally retarded persons in a Danish county.

An analytical description is presented of 942 mentally retarded persons from the county of West Zealand. The prevalence of mental retardation (i.e. persons who were registered with an IQ below 75) was 0.36%. Almost half of the patients were living in institutions. Of the patients 43% were women and 57% men. Important aetiological factors are listed. In almost one third of the patients, similar cases were present among the closest relatives; 30% of the patients were born as the fourth or subsequent child in the family; one sixth of the mothers were more than 35 years old at the birth of the handicapped child. Twenty-two percent of the patients with IQs below 50 had Down's syndrome. Seventeen percent of the patients had epilepsy had 11% cerebral palsy. In the central institution all patients had psychiatric or somatic complications.