Table 4.

Summary of diagnoses made in 595 mentally retarded institutionalized patients

Diagnosis	Number	Per cent
Diagnosis not made	253	42·5
Genetic disorders:
autosomal dominant	7	1·2
autosomal recessive	15	2·5
chromosome	39	6·6
X-linked	3	0·5
other genetic/multifactorial	64	10·8
Environmental insult	170	28·6
Birth defects	17	2·9
Diagnosis made but cause unknown	27	4·5