An aetiological study of 1,000 patients with an I.Q. assessment below 51.

This paper examines the actiological basis of the severer grades of mental retardation in 1,000 individuals attending an outpatient clinic. It was found it was possible to make a suggested diagnosis in 78% of cases. These fell into broad aetiological groups: genetically determined, 25%: early prenatal abomalies, 18%: perinatal damage, 17% prenatal and postnatal infections, 15%; cultural disintegration, 3%. The changing pattern of incidence and the possibilities of prevention are discussed for each group.