Psychiatric illness among the mildly mentally retarded.

The relationship between mental retardation and psychiatric disturbance was studied by comparing the mentally retarded in the age group 20-60 years with matched controls. The mildly retarded showed a higher degree of neuroticism but did not differ significantly from persons of higher intelligence in the frequency of mental illnesses. By contrast the severely retarded showed an increased mental morbidity, mainly in the form of chronic psychoorganic syndromes, as compared with both the mildly retarded and controls.