CAUSES AND SYMPTOMS (Mental Retardation)

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

About 30% of cases of mental retardation is caused by hereditary factors. Mental retardation may be caused by an inherited genetic abnormality, such as fragile X syndrome. Fragile X, a defect in the chromosome that determines sex, is the most common inherited cause of mental retardation. Single-gene defects such as phenylketonuria (PKU) and other inborn errors of metabolism may also cause mental retardation if they are not discovered and treated early. An accident or mutation in genetic development may also cause retardation. Example of such accidents is development of an extra.

An accident or mutation in genetic development may cause retardation. An example of such a mutation is the development of an extra chromosome 21 that cause Down syndrome.

Prenatal illness and issues

Fetal alcohol syndrome (FAS) affects one in 3,000 children in Western countries. It is caused by the mother’s heavy drinking during the first twelve weeks (trimester) of pregnancy. Some studies have shown that even moderate alcohol use during the pregnancy may cause learning disabilities in children. Drug abuse and cigarette smoking during pregnancy have also been linked to mental retardation.

Maternal infections and such illness as glandular disorders, rubella, toxoplasmosis, and cytomegalovirus (CMV) infection may cause mental retardation. When the mother has high blood pressure (hypertension) or blood poising (toxemia), the flow of oxygen to the fetus may be reduced, causing Brain damage and mental retardation.

Birth defects that cause physical deformities of the head, brain, and central nervous system frequently cause mental retardation. Neural tube defect, for example, is a birth defect in which the neural tube that forms the spinal cord does not close completely. This defect may cause children to develop an accumulation of cerebrospinal fluid inside the skull (hydrocephalus). Hydrocephalus can cause learning impairment by putting pressure on the brain.

Childhood illness and injuries

Hyperthyroidism, whooping cough, chickenpox, measles, and Hib disease

(A bacterial infection) may cause mental retardation if they are not treated adequately. An infection of the membrane conversing the brain (meningitis)

or an inflammation of the brain itself (encephalitis) can cause swelling that in turn may cause brain damage and mental retardation. Traumatic brain injury caused by a blow to the head or by violent shaking of the upper body may also cause brain damage and mental retardation in children.

Environmental factors

Ignored or neglected infants who are not provided with mental retardation and physical stimulation required for normal development may suffer irreversible learning impairment. Children who live in poverty and suffer from malnutrition, unhealthy living conditions, abuse, and improper or inadequate medical care are at a higher risk. Exposure to lead or mercury can also cause mental retardation. Many children have developed lead poisoning from eating the flaking lead-based paint often found in older building.