Table 1.

Cause of Mental Retardation Among Children Without Autism or Cerebral Palsy Enrolled With the DDS and Born in California Between 1987 and 1994

Total
(n = 16 735)
Mild MR
(n = 9227)
Severe MR
(n = 3465)
Unspecified MR
(n = 4043)
n(%)n(%)n(%)n(%)
Known cause5621(33.6)2112(22.9)1209(34.9)2300(56.9)
Chromosomal4298(25.7)1575(17.1)801(23.1)1922(47.5)
Infection/parasitic disease45(0.3)17(0.2)16(0.5)12(0.3)
Neoplasm42(0.3)26(0.3)6(0.2)10(0.3)
Endocrine or metabolic disorder135(0.8)63(0.7)36(1.0)36(0.9)
Disease of central nervous system139(0.8)44(0.5)48(1.4)47(1.2)
Central nervous system anomaly688(4.1)247(2.7)224(6.5)217(5.4)
Congenital infection70(0.4)24(0.3)22(0.6)24(0.6)
Injury/poisoning204(1.2)116(1.3)56(1.6)32(0.8)
Unknown cause11 114(66.4)7115(77.1)2256(65.1)1743(43.1)