ABSTRACT
The previous chapter was devoted to chromosomal and genetic determinants of mental retardation, events occurring at conception. We now move forward time-wise to biological causes arising after conception: during prenatal life, at or around the time of birth (perinatal-neonatal), and postnatally (Table 4.1). Nearly one half (47%) of retardation is attributed to events occurring during this time frame—32% to the prenatal period, 11% to the perinatal period, and 4% to the postnatal period (Crocker, 1992). It should be noted that, apart from the role of the young child's psychological environment as a contributor to mental retardation, discussed in the next chapter, nearly one third (30%) of retardation is of unknown origin (Crocker, 1992). The chapter concludes with a description of two major disorders often associated with mental retardation, cerebral palsy and epilepsy, and with a brief treatment of spina bifida, a condition that typically produces some degree of cognitive impairment.
