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| __NOTOC__
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| '''For patient information click [[Intellectual disability (patient information)|here]]''' | | '''For patient information click [[Intellectual disability (patient information)|here]]''' |
| {{Intellectual Disability}} | | {{Mental retardation}} |
| {{CMG}}; {{AE}}{{Chelsea}} {{KS}} | | {{CMG}}; {{AE}}{{Chelsea}} {{KS}} |
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| {{SK}} General learning disability; intellectual disability; unspecified intellectual disability | | {{SK}} General learning disability; intellectual disability; unspecified intellectual disability |
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| == [[Intellectual Disability overview|Overview]] == | | ==[[Mental retardation overview|Overview]]== |
| Intellectual disability (ID) belongs to [[neurodevelopmental]] [[disorders]] that affect [[children]] and [[adolescents]] during the [[developmental]] [[period]]. It is categorized into four subclasses that determine the need for [[support]]. This condition is characterized by [[impairments]] in both [[intellectual]] and [[adaptive]] [[functions]]. [[Research]] involving ID has found that [[genes]] that [[encode]] [[cognitive]] abilities play an essential role in its [[pathophysiology]]. An [[interplay]] of [[environment]] and [[genetics]] can cause ID, and [[comprehensive]] [[screening]] is done in these cases. More importantly, ID has existing [[co-morbid]] [[conditions]], which makes [[treatment]] and [[care]] a [[challenge]].
| | ==[[Mental retardation historical perspective|Historical Perspective]]== |
| | | ==[[Mental retardation classification|Classification]]== |
| == [[Mental retardation historical perspective|Historical Perspective]] == | | ==[[Mental retardation pathophysiology|Pathophysiology]]== |
| Intellectual disability traces its roots back to [[ancient civilizations]]. The [[Egyptians]] focused on treating [[disabilities]] and other [[ailments]], while [[Greek]] and [[Roman]] [[Civilizations]] negatively viewed [[disability]], killing those with disabilities. During the [[Middle Ages]], [[intellectual disability]] revolved around [[religion]] and [[superstitions]]. The [[Church]] became a [[refuge]] for the [[individual]] with disabilities by providing shelter. The [[Restoration period]] associated [["idiocy"]] and [[mental illness]] with [[immortality]] for which having a [[disability]] is a [[punishment]].
| | ==[[Mental retardation causes|Causes]]== |
| In the [[17th century]], [[John Locke]] differentiated intellectual disabilities from [[physical ones]], where both [[mental]] and [[emotional]] [[deficits]] characterized [[intellectual]] [[disabilities]]. [[Oxford]] [[Philosopher]] [[Willis]] pinpointed various [[etiologies]] for a [[mental disability]] such as [[heredity]], [[trauma]], other [[diseases]], and [[spirits]]. <ref name="RothSarawgi2019">{{cite journal|last1=Roth|first1=Emily A.|last2=Sarawgi|first2=Shivali N.|last3=Fodstad|first3=Jill C.|title=History of Intellectual Disabilities|year=2019|pages=3–16|issn=2192-922X|doi=10.1007/978-3-030-20843-1_1}}</ref>
| | ==[[Mental retardation differential diagnosis|Differentiating Mental retardation from other Diseases]]== |
| | | ==[[Mental retardation epidemiology and demographics|Epidemiology and Demographics]]== |
| == [[Intellectual Disability classification|Classification]] == | | ==[[Mental retardation risk factors|Risk Factors]]== |
| The [[DSM 5]] Classification of Severity for Intellectual disability has veered away from [[IQ scores]] and now considers [[adaptive]] [[functioning]] as the basis for classification.<ref name="PatelApple2018">{{cite journal|last1=Patel|first1=Dilip R.|last2=Apple|first2=Roger|last3=Kanungo|first3=Shibani|last4=Akkal|first4=Ashley|title=Intellectual disability: definitions, evaluation and principles of treatment|journal=Pediatric Medicine|volume=1|year=2018|pages=11–11|issn=26175428|doi=10.21037/pm.2018.12.02}}</ref> <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref>
| | ==[[Mental retardation screening|Screening]]== |
| {| class="wikitable" style="text-align:center"
| | ==[[Mental retardation natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
| |+Classification of Intellectual Disability
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| !Severity Level!![[Conceptual]] Skills!![[Social]] Skills!![[Practical]] Skills
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| !Mild
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| | Individuals can grasp simple [[mathematical]] [[operations]] like [[multiplication]] and [[division]], [[write]] [[letters]] and [[lists]]; however, they have difficulty with [[complex]] [[tasks]] such as [[planning]], [[strategizing]], and [[abstract thinking]].|| They have difficulty interpreting [[social cues]], and there is risk for [[manipulation]]. || They can do [[essential]] [[self-care]] and [[home]] [[activities]] as well as [[job]] [[applications]] but may require some [[support]] in [[banking]], [[transportation]] and even [[raising]] a [[family]].
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| !Moderate
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| |[[Academic]] [[skill]] [[development]] is markedly slowed compared to [[peers]] and [[adults]] attain [[elementary]] level of [[knowledge]]. They can do [[basic]] [[skills]] like [[copy]] [[address]] and basic [[reading]]. || There is a considerable gap in [[social skills]] compared to [[peers]]. They need constant [[support]] to succeed in [[communications]] in the [[work]] [[setting]]. || There is some [[independence]] in [[self-care]] and [[house chores]] with [[constant]] [[reinforcement]].
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| !Severe
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| | [[Language]], [[arithmetic]], the [[concept]] of [[time]], and [[money]] are markedly limited, and they need constant [[support]] in [[life]]. || [[Speech]] is characterized by [[simple]] [[phrases]] and [[words]]. || [[Constant]] support in all [[activities of daily living| ADL]] is needed as they may also have [[motor]] [[comorbidities]].
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| !Profound
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| | Very limited [[communication]] [[skills]] but may acquire [[visuospatial]] [[skills]] such as [[matching]] and [[sorting]]. || The individual communicates through [[non-verbal]] means and there may also be [[co-morbid]] [[motor]] and [[sensory]] [[impairments]]. || Require daily supervision across a lifetime.
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| |}
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| == [[Intellectual Disability pathophysiology|Pathophysiology]] ==
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| Intellectual disorders with intact [[cortex]] have found that most of the known [[genes]] influencing [[cognitive]] [[abilities]] are [[X-linked]]. These [[genes]] [[code]] for different [[proteins]] and some are involved in [[neuronal]] [[connectivity]] and [[synapse]] formation and activity.
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| Recent progress in unraveling the [[pathophysiology]] of ID involves defects in [[synaptogenesis]] and [[synaptic]] activities, including [[neuroplasticity]].
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| An important [[finding]] that [[illustrates]] the importance of [[synapses]] in the occurrence of ID involves the [[FMRP]] [[protein]] that is absent in [[Fragile X syndrome]]. The [[FMRP]] [[protein]] is normally detected in the [[nucleus]], [[body]], and [[dendrites]]. It is [[upregulated]] by [[glutamate]]-mediated [[stimulation]]—the specific [[knockout]] of [[Fmr1]] results in abnormal [[morphology]] of [[dendrites]] in [[Purkinje cells]] in the [[cerebellum]]. Therefore, defects in [[synaptic]] structure and overall [[neuronal]] [[connectivity]] impairs proper [[information]] [[processing]]. <ref name="ChellyKhelfaoui2006">{{cite journal|last1=Chelly|first1=Jamel|last2=Khelfaoui|first2=Malik|last3=Francis|first3=Fiona|last4=Chérif|first4=Beldjord|last5=Bienvenu|first5=Thierry|title=Genetics and pathophysiology of mental retardation|journal=European Journal of Human Genetics|volume=14|issue=6|year=2006|pages=701–713|issn=1018-4813|doi=10.1038/sj.ejhg.5201595}}</ref> <ref name="KoekkoekYamaguchi2005">{{cite journal|last1=Koekkoek|first1=S.K.E.|last2=Yamaguchi|first2=K.|last3=Milojkovic|first3=B.A.|last4=Dortland|first4=B.R.|last5=Ruigrok|first5=T.J.H.|last6=Maex|first6=R.|last7=De Graaf|first7=W.|last8=Smit|first8=A.E.|last9=VanderWerf|first9=F.|last10=Bakker|first10=C.E.|last11=Willemsen|first11=R.|last12=Ikeda|first12=T.|last13=Kakizawa|first13=S.|last14=Onodera|first14=K.|last15=Nelson|first15=D.L.|last16=Mientjes|first16=E.|last17=Joosten|first17=M.|last18=De Schutter|first18=E.|last19=Oostra|first19=B.A.|last20=Ito|first20=M.|last21=De Zeeuw|first21=C.I.|title=Deletion of FMR1 in Purkinje Cells Enhances Parallel Fiber LTD, Enlarges Spines, and Attenuates Cerebellar Eyelid Conditioning in Fragile X Syndrome|journal=Neuron|volume=47|issue=3|year=2005|pages=339–352|issn=08966273|doi=10.1016/j.neuron.2005.07.005}}</ref>
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| == [[Mental retardation causes|Causes]] == | |
| In less than 50% of individuals with [[mild]] ID, a specific cause is identified, and it increases to 75% in those with [[severe]] ID. <ref name="MoeschlerShevell2014">{{cite journal|last1=Moeschler|first1=J. B.|last2=Shevell|first2=M.|title=Comprehensive Evaluation of the Child With Intellectual Disability or Global Developmental Delays|journal=PEDIATRICS|volume=134|issue=3|year=2014|pages=e903–e918|issn=0031-4005|doi=10.1542/peds.2014-1839}}</ref>
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| ===Genetics===
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| [[Down syndrome]] [[(Trisomy 21)]] is the most common [[genetic]] [[cause]] of ID, while [[Fragile X]] is the most common [[inherited]] [[cause]] of ID.
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| <ref name="MoeschlerShevell2014">{{cite journal|last1=Moeschler|first1=J. B.|last2=Shevell|first2=M.|title=Comprehensive Evaluation of the Child With Intellectual Disability or Global Developmental Delays|journal=PEDIATRICS|volume=134|issue=3|year=2014|pages=e903–e918|issn=0031-4005|doi=10.1542/peds.2014-1839}}</ref>
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| ===Environmental Factors===
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| [[Alcohol]] [[exposure]] during [[pregnancy]], [[lead]] and other [[heavy metals]], [[iodine deficiency]], [[brain infections]], [[congenital rubella syndrome]], and [[cytomegalovirus infections]], as well as [[hypoxic-ischemic injury]], and [[periventricular hemorrhages]] all cause [[brain injury]] resulting in [[disability]]. {{cite web |url=http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A163146&dswid=-7424 |title=Intellectual Disability and Mental Health Problems : Evaluation of Two Clinical Assessment Instruments, Occurrence of Mental Health Problems and Psychiatric Care Utilisation |format= |work= |accessdate=}}
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| == [[Mental retardation differential diagnosis|Differentiating Mental retardation from other Diseases]] == | |
| #[[Neurocognitive disorders]] – there is loss of [[cognitive]] functioning in these cases.
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| #[[Specific learning disorder]] and [[language disorders]] – compared to individuals with ID, these individuals have [[deficits]] in [[communication]] and [[learning]] aspects but with [[normal]] [[intellect]] and [[adaptive]] [[function]].
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| #[[Autism spectrum disorder]] – [[social development]] and [[language]] [[deficits]] are the [[hallmark]] of [[autism]] spectrum patients and have [[normal]] [[motor]] [[development]].
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| Possible hearing and visual impairments should be ruled out in diagnosing intellectual disability. <ref name="PatelApple2018">{{cite journal|last1=Patel|first1=Dilip R.|last2=Apple|first2=Roger|last3=Kanungo|first3=Shibani|last4=Akkal|first4=Ashley|title=Intellectual disability: definitions, evaluation and principles of treatment|journal=Pediatric Medicine|volume=1|year=2018|pages=11–11|issn=26175428|doi=10.21037/pm.2018.12.02}}</ref> <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref>
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| == [[Intellectual Disability epidemiology and demographics|Epidemiology and Demographics]] == | |
| The [[prevalence]] is 1% in the general [[population]], with 6 per 1000 persons having a [[severe]] [[mental disability]]. In the United States, individuals with a [[severe]] [[intellectual disability]] are at 0.3-0.5%, while worldwide [[prevalence]] is at 16.41 per 1000 people in [[developing countries]] and 9.21 per 1000 people in [[developed countries]]. [[Males]] are more likely to have a [[mental disability]] with a ratio of 2:1, and [[families]] with one child with [[severe]] [[mental disability]] have a [[recurrence risk]] of 3% and 9%. <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref> <ref name="MaulikMascarenhas2011">{{cite journal|last1=Maulik|first1=Pallab K.|last2=Mascarenhas|first2=Maya N.|last3=Mathers|first3=Colin D.|last4=Dua|first4=Tarun|last5=Saxena|first5=Shekhar|title=Prevalence of intellectual disability: A meta-analysis of population-based studies|journal=Research in Developmental Disabilities|volume=32|issue=2|year=2011|pages=419–436|issn=08914222|doi=10.1016/j.ridd.2010.12.018}}</ref>
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| == [[Mental retardation risk factors|Risk Factors]] == | |
| [[Prenatal]] causes <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref>
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| #[[Genetic]] [[syndromes]]
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| #[[Inborn errors of metabolism]]
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| #[[Brain malformations]]
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| #[[Maternal disease]]
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| #[[Environmental]] factors such as the [[history]] of [[alcoholism]], [[teratogens]], and other [[drugs]]
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| [[Perinatal]] [[causes]] include events during [[labor]] and [[delivery]] that ultimately lead to [[ischemic injury]] to [[neonates']] [[brains]]. <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref>
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| [[Postnatal]] causes <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref>
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| #[[Hypoxic-ischemic injury]]
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| #[[Traumatic brain injury]]
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| #[[Infections]]
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| #[[Demyelinating]] [[disorders]]
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| #[[Infantile spasms]]
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| #[[Severe]] and [[chronic social deprivation]]
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| #[[Heavy metal poisoning]]
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| #[[Toxic metabolic syndromes]]
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| == [[Intellectual Disability screening|Screening]] ==
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| Evaluation is dependent on [[age]] at [[onset]], the [[severity]] of [[signs]] and [[symptoms]], and the need to determine the underlying [[etiology]] of ID. A [[comprehensive ]][[screening]] includes [[clinical assessment]] paying particular attention to [[prenatal]] and [[perinatal]] history and [[family pedigree]], [[psychological testing]], [[karyotyping]] and [[metabolic]] [[screening]], as well as [[neuroimaging]] tests. <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref> {{cite web |url=https://www.aaidd.org/docs/default-source/default-document-library/idd-d-20-00058_r28c0757ae9e8c6329b425ff0000b6faa6.pdf?sfvrsn=e78b3421_0 |title=www.aaidd.org |format= |work= |accessdate=}}
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| <ref name="MoeschlerShevell2014">{{cite journal|last1=Moeschler|first1=J. B.|last2=Shevell|first2=M.|title=Comprehensive Evaluation of the Child With Intellectual Disability or Global Developmental Delays|journal=PEDIATRICS|volume=134|issue=3|year=2014|pages=e903–e918|issn=0031-4005|doi=10.1542/peds.2014-1839}}</ref>
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| ===Intelligence assessment=== | |
| [[Intelligence Quotient]] [[(IQ)]] is the standard for estimating [[intellectual function]]. [[Standardized]] [[tools]] such as the [[Wechsler scale]] is administered to children 6-16 years old, while a brief [[]assessment tool]] such as the [[Kauffman Brief Intelligence Test]] is an alternative if the [[Wechsler test]] is not possible. The mean value of [[IQ]] is 100, and 70-75 represents the upper limit of two [[standard deviations]] below the [[mean]]. Several factors may [[influence]] [[intelligence assessment]], and this includes [[measurement error]], [[Flynn effect]], [[practice effects]], [[outliers]], and [[test]] [[selection]], to name a few. <ref name="MoeschlerShevell2014">{{cite journal|last1=Moeschler|first1=J. B.|last2=Shevell|first2=M.|title=Comprehensive Evaluation of the Child With Intellectual Disability or Global Developmental Delays|journal=PEDIATRICS|volume=134|issue=3|year=2014|pages=e903–e918|issn=0031-4005|doi=10.1542/peds.2014-1839}}</ref> <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref> | |
| ===Adaptive function assessment===
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| The [[Vineland Adaptive Behavior Scale]] evaluates [[communication]], ability to perform [[activities of daily living (ADL)]], [[motor]] and [[socialization]]. Another [[assessment tool]] is [[AAIDD's Diagnostic Adaptive Behavior Scale (DABS)]], administered to individuals 4-21 years old. This tool focuses on the "cut-off" area for ruling in a diagnosis of ID to determine eligibility for [[special education]] services, [[social security]] [[benefits]], and [[home]] and [[community-based]] [[waiver services]]. <ref name="NavasZhang2016">{{cite journal|last1=Navas|first1=Patricia|last2=Zhang|first2=Dalun|last3=Widaman|first3=Keith F.|last4=Spreat|first4=Scott|last5=Borthwick-Duffy|first5=Sharon A.|last6=Bersani|first6=Henry (Hank)|last7=Balboni|first7=Giulia|last8=Thissen|first8=David|last9=Schalock|first9=Robert L.|last10=Tassé|first10=Marc J.|title=Development and Standardization of the Diagnostic Adaptive Behavior Scale: Application of Item Response Theory to the Assessment of Adaptive Behavior|journal=American Journal on Intellectual and Developmental Disabilities|volume=121|issue=2|year=2016|pages=79–94|issn=1944-7558|doi=10.1352/1944-7558-121.2.79}}</ref> <ref name="ZhangWidaman2012">{{cite journal|last1=Zhang|first1=Dalun|last2=Widaman|first2=Keith F|last3=Thissen|first3=David|last4=Spreat|first4=Scott|last5=Borthwick-Duffy|first5=Sharon A|last6=Bersani|first6=Hank|last7=Balboni|first7=Giulia|last8=Schalock|first8=Robert L|last9=Tassé|first9=Marc J|title=The Construct of Adaptive Behavior: Its Conceptualization, Measurement, and Use in the Field of Intellectual Disability|journal=American Journal on Intellectual and Developmental Disabilities|volume=117|issue=4|year=2012|pages=291–303|issn=1944-7558|doi=10.1352/1944-7558-117.4.291}}</ref>
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| ===Genetic and Metabolic Testing===
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| [[Newborn screening]] programs [[screen]] for [[inborn errors of metabolism]] with a yield of < 1%, and [[chromosomal analysis]] is required in children with unknown causes of ID with a yield of 12%. While [[genetic]] tests help discern the [[prognosis]] and [[treatment plan]], it should be taken into account that these are expensive, and the findings may not reflect the [[phenotype]] of an individual. <ref name="PatelApple2018">{{cite journal|last1=Patel|first1=Dilip R.|last2=Apple|first2=Roger|last3=Kanungo|first3=Shibani|last4=Akkal|first4=Ashley|title=Intellectual disability: definitions, evaluation and principles of treatment|journal=Pediatric Medicine|volume=1|year=2018|pages=11–11|issn=26175428|doi=10.21037/pm.2018.12.02}}</ref>
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| == [[Intellectual Disability natural history, complications and prognosis|Natural History, Complications and Prognosis]] ==
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| ID often is accompanied by other [[mental]], [[medical]], and [[physical]] conditions like [[epilepsy]] and [[cerebral palsy]]. The most common [[comorbid]] [[conditions]] are [[attention deficit hyperactivity disorder]] [[(ADHD]], [[depression]], [[bipolar disorder]], [[anxiety disorder]], [[autism spectrum disorder]], and [[stereotypical]] [[movement]] disorder. <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref>
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| ==Diagnosis== | | ==Diagnosis== |
| The [[DSM 5]] Diagnostic Criteria specifies that all of the three criteria must be satisfied: <ref>{{cite journal|title=Neurodevelopmental Disorders|year=2013|doi=10.1176/appi.books.9780890425596.dsm01}}</ref>
| | [[Mental retardation diagnostic study of choice|Diagnostic study of choice]] | [[Mental retardation history and symptoms|History and Symptoms]] | [[Mental retardation physical examination|Physical Examination]] | [[Mental retardation laboratory findings|Laboratory Findings]] | [[Mental retardation electrocardiogram|Electrocardiogram]] | [[Mental retardation x ray|X-Ray Findings]] | [[Mental retardation echocardiography and ultrasound|Echocardiography and Ultrasound]] | [[Mental retardation CT scan|CT-Scan Findings]] | [[Mental retardation MRI|MRI Findings]] | [[Mental retardation other imaging findings|Other Imaging Findings]] | [[Mental retardation other diagnostic studies|Other Diagnostic Studies]] |
| #Individuals have difficulty in [[executive functioning]], [[academic]] [[learning]], and [[experiential]] [[learning]] confirmed by [[standard]] [[assessment tools]] and [[clinically]].
| | ==Treatment== |
| #[[Social communication]] [[skills]] are challenging and [[practical skills]] that impair independence (performing [[activities of daily living]]) and [[interaction]] with other people.
| | [[Mental retardation medical therapy|Medical Therapy]] | [[Mental retardation interventions|Interventions]] | [[Mental retardation surgery|Surgery]] | [[Mental retardation primary prevention|Primary Prevention]] | [[Mental retardation secondary prevention|Secondary Prevention]] | [[Mental retardation cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Mental retardation future or investigational therapies|Future or Investigational Therapies]] |
| #It happens during the [[developmental period]].
| | ==Case Studies== |
| The classification of ID must also be specified.
| | [[Mental retardation case study one|Case #1]] |
| | | ==References== |
| == Treatment == | | {{Reflist}} |
| Treatment should address the underlying [[cause]] of ID, treatment of [[comorbid]] [[physical]] [[disorders]] that may further impair functioning, such as [[pharmacologic]] [[treatment]] for [[behavioral]] disorders in [[Fragile X]] patients, and institution of [[special education]], [[rehabilitation]], and [[psychosocial]] [[interventions]]. <ref name="HagermanPolussa2015">{{cite journal|last1=Hagerman|first1=Randi J.|last2=Polussa|first2=Jonathan|title=Treatment of the psychiatric problems associated with fragile X syndrome|journal=Current Opinion in Psychiatry|volume=28|issue=2|year=2015|pages=107–112|issn=0951-7367|doi=10.1097/YCO.0000000000000131}}</ref> {{cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK332877/ |title=Clinical Characteristics of Intellectual Disabilities - Mental Disorders and Disabilities Among Low-Income Children - NCBI Bookshelf |format= |work= |accessdate=}}
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| == References ==
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| {{Reflist}}
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| [[Category:Psychiatry]] | | [[Category:Psychiatry]] |
| [[Category:Disability]] | | [[Category:Disability]] |