The causes of mental retardation can be divided into biomedical, social behavioral and educational risk factors that interact during the life of an individual and /or across generations from parent to child. Biomedical factors are related to biologic process, such as genetic disorders or nutrition. Social factors are related to social and family interaction, such as child stimulation and adult responsiveness. Behavioral factors are related to harmful behaviors, such as mental substance abuse. And educational factors are related to harmful behaviors, such as family and educational supports that promote mental development and increases in adaptive skills. Also, factors present during one generation can influence the outcomes of the next generation. By understanding inter-generational causes appropriate supports can be used to prevent and reverse the effects of risk factors
Causes and Symptoms
Low IQ scores and limitations in adaptive skills are the hallmarks of mental retardation. Aggression, self-injury, and mood disorders are sometimes associated with the disability. The severity of the symptoms and the age at which they first appear depend on the cause. Children who are mentally retarded reach developmental milestones significantly later than expected, if at all. If retardation is caused by chromosomal or other generic disorders, it is often apparent from infancy. If retardation is caused by childhood illness or injuries, learning and adaptive skills that were once easy may suddenly become difficult or impossible to master.
In about 40% of cases, the cause of mental retardation cannot be found. Biological and environmental factors that can cause mental retardation include:
Genetic Factors
Prenatal illness and issues
Childhood illness and injuries
Environmental factors
Demographics
The prevalence of metal retardation in North America is a subject of heated debate. It is thought to be between 3%-5% depending upon the population, methods of assessment, and criteria of assessment that are used. Many people believe that the actual prevalence is probably closer to 1% and that the 3% figure is accepted, however, it means that 2.5 million mentally retarded people reside in the United States. The three most common causes of mental retardation, accounting for about 30% of cases, are Down syndrome, fragile X, and fetal alcohol syndrome. Males are more likely than females to have MR in a 1.5:1 ratio.
