RT Journal Article SR Electronic T1 The recurrence risks for mild idiopathic mental retardation. JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP 260 OP 266 DO 10.1136/jmg.26.4.260 VO 26 IS 4 A1 S Bundey A1 A Thake A1 J Todd YR 1989 UL http://jmg.bmj.com/content/26/4/260.abstract AB A genetic study of children attending ESN(M) schools in Coventry has shown a recurrence risk of idiopathic mental retardation in sibs lying between 1 in 4 and 1 in 5. There was also a prevalence of mental retardation in other relatives that was greater than the population prevalence, and was less for second degree relatives than for first degree, and less still for third degree relatives. Recurrence in sibs was greater if more than one first degree relative was affected. There was no suggestion of a contribution by X linked genes, once the fragile X syndrome had been excluded. The presence of perinatal and other environmental factors in the index children did not alter the recurrence risk for sibs except for very low birth weight. There was a low recurrence rate of mental retardation in Asian families, suggesting that they had a different distribution of intelligence from non-Asian families.