[Epidemiology of mental deficiency. The study of Safor (I): prevalence and etiology].

An epidemiological study of Mental Deficiency was carried out in an area of the region of Valencia. A prevalence of children between 0-14 years old were found to have an IQ of below 70; 14,10 every 1,000 over a period from september 1987 to june 1988. This prevalence increases gradually according to age, reaching a high point at 10 and another at 14. These fluctuations are due to extreme and less serious cases. 29% of the cases can be attributed to prenatal causes. 9% are perinatal, and 49% are a postnatal origin. In 57% of the cases no cause has been found, and can be considered of unknown etiology.