Delay in development of language skills, adaptive skills and cognitive skills mark the onset of intellectual disability. In mild cases, signs and symptoms may not be noticeable until the child reaches preschool age. The following are some of the important markers noticed in affected children:

• Inability to speak mama/dada in the first year
• Child does not say 2 word phrases by the age of 2 years
• Delay in motor adaptive skills such as child does not dress up or practices such as self-feeding and or toileting are absent
• Delay in cognitive development, marked by inability of the child to follow instructions and lack of problem solving skills
• Behavioral disturbances are noticeable such as hyperactivity, disturbance in sleep and colic

Based on the guidelines provide by the Diagnostic and Statistical Manual of Mental Disorders, the child should meet the following three criteria to be diagnosed with intellectual disability.

• Limitations in adaptive behavior such as interpersonal skills, communication and self-help skills
• Deficits in mental abilities
• Signs and symptoms become evident early in life

The first 2 factors can be diagnosed by measuring the IQ score. The third factor is important to determine, in order to rule out other disorders like Alzheimer disease which share similar signs and symptoms, but have a late onset.

An IQ score of below 70 indicate mental retardation and is done at the preliminary level. This is followed by other methods such as adaptive behavior rating scale and Denver developmental screening test [8].

Brain imaging tests are also indicated in children with intellectual disability. A MRI scan of brain is preferred, because it enables better assessment of abnormalities of central nervous system [9].

Treatment is geared towards maximum development of the child’s potential. Therapists and specialized educators help in fulfilling such goals. They help in developing the social skills of the child so that they learn to communicate effectively and put forth their problems and thoughts to the outside world. Behavior counseling forms an important part of the treatment regime to help the child to deal with their mood swings and sometimes aggressive nature.

Pharmacologic treatment is of little help in improving the cognitive functioning. However, the drug donezepil has been found to be effective in improving the cognitive function in children with Down syndrome. Parents might also think of enrolling their children in various support groups for proper grooming [10].

Prognosis of the condition would largely depend on the underlying etiology, severity of the disease and type of treatment methods administered. In many cases it has been seen that, affected individuals lead a productive life and learn to carry out many tasks on their own. With proper learning and education, children can function properly and can be successful in life [7].

Amongst the various etiologies, Down syndrome, fetal alcohol syndrome and velocariofacial syndrome are the major causative factors [2]. In about one third to the half of all cases, the exact cause behind development of mental retardation is not known [3].

The following causes are known to trigger the onset of mental retardation:

• Infections that occur during birth or after it
• Chromosomal abnormalities
• Malnutrition during pregnancy 
• Alcohol consumption during pregnancy can cause improper fetal development
• Exposure to disease conditions such as measles, pertussis and meningitis
• Iodine deficiency 
• Absence of arcuate fasciculus

Mental retardation affects about 1 – 3% of the total population. The prevalence rate of severe form of intellectual disability has been estimated to occur in 6 per 1,000 population [4].

It has been assessed that, about 75 – 90% of individuals suffer from mild form intellectual disability. Of these, non-syndromic intellectual disability occurs in about 30 – 50% of cases. Boys are found to be more affected than girls, for both mild and severe form of the disease. Mortality rates at an early age have been found to be higher in children suffering from Down syndrome [5].

Mental retardation primarily occurs as the outcome of several disorders of the central nervous system. In majority of the cases, no significant structural abnormalities have been noticed in individuals with mild intellectual disability. However, in severe cases, malformations of the central nervous system include hydranencephaly, neural tube defects and microcephaly. Certain studies have indicated a link between poor cognitive functioning and poverty; however the etiologic contribution still remains unclear [6].

Some of the risk factors such as alcohol consumption during pregnancy, avoiding toxin exposure and iodine deficiency can go a long way in preventing the onset of mental retardation. Getting vaccinated against infectious diseases such as rubella can also help prevent mental retardation from setting in. Proper genetic counseling during pregnancy can help parents take informed decisions.

The condition is diagnosed before one reaches 18 years. Individuals suffering from mental retardation lack in appropriate mental development and do not have the ability to adapt and learn new things. Intellectual disability is further classified into 2 categories: non-syndromic intellectual disability and syndromic intellectual disability [1].

• Definition: Mental retardation, also known as intellectual disability, is a type of neuro-developmental disorder, wherein there is impairment of adaptive functioning and intellectual skills. Affected individuals have an IQ score of 70 or below.
• Cause: Various disease conditions such as Down syndrome, fetal alcohol syndrome and velocariofacial syndrome predisposes children to develop intellectual disability. In addition, various other risk factors include alcohol consumption during pregnancy, exposure to toxins, infectious diseases, iodine deficiency, chromosomal abnormalities and malnutrition.
• Symptoms: Signs and symptoms of intellectual disability include delay in development of cognitive skills, motor skills, language delays, continuation of infant type behavior till late years, difficulty in following instructions and aggressive behavior.
• Diagnosis: Diagnosis includes assessing the IQ score and testing the adaptive behavior of the individual with help of adaptive behavior rating scale. In addition, imaging studies like CT scan and MRI of brain is also required to assess abnormalities.
• Treatment: Treatment is geared towards developing the potential of the children as much as possible. This is done by therapists and specialized educators who provide training and behavior counseling to help develop their skills. Some medications such as donezepil have been found to be effective for patients with Down syndrome; it helps improve their cognitive functioning.

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