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Mental Retardation


Mental retardation, which is now renamed as intellectual disability, is a type of neuro-developmental disorder, wherein the affected individuals have poor adaptive functioning along with impaired intellectual development. Individuals with an IQ score below 70 and a significant deficit observed in adaptive behaviors that interferes with general living are considered to be mentally retarded.


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
Down Syndrome
  • Some medications such as donezepil have been found to be effective for patients with Down syndrome; it helps improve their cognitive functioning.[symptoma.com]
  • The characteristic phenotype of Down syndrome is basically the same in trisomy 21 and in translocation.[emedicine.com]
  • The increase in death rate from age 40 years was steeper in patients with Down syndrome than in those without Down syndrome. [10] Mortality/Morbidity MR/ID itself is not necessarily associated with an increased premature death rate.[emedicine.medscape.com]
  • ., Down syndrome Down syndrome, congenital disorder characterized by mild to severe mental retardation, slow physical development, and characteristic physical features.[encyclopedia2.thefreedictionary.com]
Cerebral Palsy
  • palsy (n 100, 2.0%).[ncbi.nlm.nih.gov]
  • palsy ( n 100, 2.0%).[doi.org]
  • Depending on the specific cause of the mental disability, such as cerebral palsy or autism, the numbers may vary. It is important to know, however, that you and your loved one are not alone.[qualityrespiteandhomecareinc.com]
  • Economic costs of mental retardation, cerebral palsy, hearing loss, and vision impairment. In: Altman BM, Barnartt SN, Hendershot G, Larson S, eds.[cdc.gov]
Progressive Mental Retardation
  • Affected males showed non-specific, non-progressive mental retardation ranging from severe to moderate, without seizures, whereas carrier females showed highly variable cognitive capacities, ranging from moderate mental retardation to normal intelligence[latunisiemedicale.com]
Recurrent Respiratory Infections
  • The proband and his cousin showed severe MR, muscular hypotonia, recurrent respiratory infections and various other features characteristic of MECP2 duplication syndrome.[ncbi.nlm.nih.gov]
Recurrent Infection
Failure to Thrive
  • The patient presented with exocrine pancreatic insufficiency as well as failure-to-thrive. On dysmorphological examination, she was noted to have an abnormal hair pattern with frontal upsweep and alae nasi hypoplasia.[ncbi.nlm.nih.gov]
  • Translated by Apolline Morville B.2 Failure to thrive or weight faltering in a primary health care setting (824 KB PDF) Astrid Berg VERSION IN FRENCH: “ Retard de croissance ou prise de poids hésitante en contexte de soin de santé primaire ” (1.27 MB[web.archive.org]
Poor Oral Hygiene
  • CONCLUSION: The deteriorated teeth condition and deprived periodontal health of MR patients may be most likely caused by the poor oral hygiene and may be worsen with the severity of the MR.[ncbi.nlm.nih.gov]
  • Abstract Hyperactivity syndromes and disorders (ADHD and HKD) include the symptoms of overactivity, inattention, and impulsivity, which occur in many other mental disorders as well, including mental retardation (MR).[ncbi.nlm.nih.gov]
  • There is social withdrawal in both the disorders but in autism there is inability of communication due to delayed impulse transmission whereas in mental retardation there is loss of cerebral functioning responsible for all poor development of all skills[differencebetween.net]
  • Mentally retarded children suffer from poor impulse control and react to simple situations aggressively.[momjunction.com]
  • […] interacting with others If your child has ID, they will probably experience some of the following behavioral issues: aggression dependency withdrawal from social activities attention-seeking behavior depression during adolescent and teen years lack of impulse[healthline.com]
  • Retarded children are prone to behavioral problems caused by short attention span, low tolerance for frustration, and poor impulse control.[healthofchildren.com]
Inappropriate Sexual Behavior
  • Some common behaviors associated with Alzheimer’s disease are rapid mood changes, crying, anger, pacing, wandering, doing things over and over, asking the same question, following people closely and inappropriate sexual behaviors.[services.dpw.state.pa.us]
  • Our case provides evidence for an association of primary amenorrhea and mental retardation with concomitant unbalanced X-autosome translocation and X chromosome rearrangement.[ncbi.nlm.nih.gov]
Primary Amenorrhea
  • Our case provides evidence for an association of primary amenorrhea and mental retardation with concomitant unbalanced X-autosome translocation and X chromosome rearrangement.[ncbi.nlm.nih.gov]
  • […] sitting up and walking Late start in talking or difficulty in talking Late in getting potty trained, doing activities like dressing or feeding independently Difficulty in remembering things or associating actions with corresponding consequences Throwing tantrums[newhealthguide.org]
  • […] walking late Talking late or having trouble with talking Slow to master things like potty training, dressing, and feeding himself or herself Difficulty remembering things Inability to connect actions with consequences Behavior problems such as explosive tantrums[webmd.com]
  • . • H/o temper tantrums, hyperkinesis, self destructive behaviour. • Any h/o physical & psychological abuse. • Lead exposure. 18.[slideshare.net]
  • Seemingly violent but harmless behaviour (often interpreted as aggression). [ 6 ] Temper tantrums. Criminal activity. Sleep disorders. Communication [ 1 ] Focus on abilities and not disabilities.[web.archive.org]
  • The cornea is the clear (transparent) outer layer of the eye, and has two functions – it protects the rest of the eye from dust, germs and other harmful or irritating material, and it acts as the eye’s outermost lens, bending incoming light onto the inner[rarediseases.org]
  • But I'm glad to see that non-disabled people are beginning to understand why less offensive words such as 'special', 'brave' and 'wheelchair-bound' are so irritating to many disabled people.[web.archive.org]
  • Fecal transplant is used to treat gut infections and is now being studied as a treatment for obesity, urinary tract infections, irritable bowel syndrome and more.[nytimes.com]
  • Buspirone in the management of anxiety and irritability in children with pervasive developmental disorders: results of an open-label study. J Clin Psychiatry. 1998 ; 59 : 56 – 59 Kowatch RA, DelBello MD.[doi.org]
  • The studies that do exist indicate that benefits vary, and significant adverse events, such as severe social withdrawal, increased crying, drowsiness, and irritability, have been noted, especially at higher doses of methylphenidate (0.6 mg/kg). [7] The[emedicine.com]
Delayed Milestone
  • In mental retardation, the child tends to have delayed milestones and will be slow in talking and walking. The low IQ restricts the memory and children have lower than average learning abilities and problem solving skills.[differencebetween.net]
  • milestones, especially language development Behavioral phenotype may also aid diagnosis as course evolves Cytogenetic studies; brain imaging; metabolic studies Will vary considerably based on etiology (if it can be established) and/or severity Diagnostic[aafp.org]


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:


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].

Sex distribution
Age distribution


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].

Patient Information

  • 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.



  1. Biscaldi M, Rauh R, Irion L, Jung NH, Mall V, Fleischhaker C, et al. Deficits in motor abilities and developmental fractionation of imitation performance in high-functioning autism spectrum disorders. Eur Child Adolesc Psychiatry. Oct 2 2013
  2. American Academy of Pediatrics Committee on Genetics. Health Supervision for Children with Down Syndrome. Pediatrics. February 2001,;volume 107, number 2,:pages 442-449
  3. Croen LA, Grether JK, Selvin S. The epidemiology of mental retardation of unknown cause. Pediatrics 2001; 107:E86.
  4. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders.5th Edition. Washington, DC: APA Press; 2013.
  5. Kaufman L, Ayub M, Vincent JB. The genetic basis of non-syndromic intellectual disability: a review. J NeurodevDisord 2010; 2:182.
  6. Ramer JC, Miller G. Overview of Mental Retardation. In: Static Encephalopathies of Infancy and Childhood, Miller G, Ramer JC (Eds), Raven Press, New York 1992.
  7. vanKarnebeek CD, Scheper FY, Abeling NG, et al. Etiology of mental retardation in children referred to a tertiary care center: a prospective study. Am J Ment Retard 2005; 110:253.
  8. Majnemer A, Shevell MI. Diagnostic yield of the neurologic assessment of the developmentally delayed child. J Pediatr 1995; 127:193.
  9. Bouhadiba Z, Dacher J, Monroc M, et al. [MRI of the brain in the evaluation of children with developmental delay]. J Radiol 2000; 81:870.
  10. McConkey R, Kelly F, Mannan H, Craig S. Moving from family care to residential and supported accommodation: national, longitudinal study of people with intellectual disabilities. Am J Intellect Dev Disabil 2011; 116:305.

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Last updated: 2019-07-11 21:26