Pediatric Intellectual Disability

Updated: Dec 03, 2018
  • Author: C Simon Sebastian, MD; Chief Editor: Caroly Pataki, MD  more...
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Intellectual Disability: What it is and What it is Not


A diagnosis of intellectual disability (ID) carries with it certain unique treatment needs that must be understood and addressed. Unfortunately, most psychiatrists are ill-equipped to handle this situation, having received little or no formal training in this area. This article is written with the specific goal of giving psychiatrists a better understanding of the special needs of patients with intellectual disability and strategies for improving their quality of life.

Intellectual disability is a state of developmental deficit, beginning in childhood, that results in significant limitation of intellect or cognition and poor adaptation to the demands of everyday life. As noted by Esquirol, intellectual disability is not a disease in and of itself, but is the developmental consequence of some pathogenic process. [1]

The American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, (DSM-5), characterizes intellectual disability (intellectual developmental disorder) by deficits in general mental abilities, such as reasoning, problem solving, planning, abstract thinking, judgment, academic learning, and learning from experience. The deficits result in impairments to adaptive functioning, such that the individual fails to meet standards of personal independence and social responsibility in one or more aspects of daily life, including communication, social participation, academic or occupational functioning and personal independence at home or in community settings. [2]

The causes of ID can be grouped from most to least common as follows:

  • Alterations in embryonic development, such as those caused by chromosomal abnormalities or fetal exposure to drugs or toxins

  • Environmental deprivation and other mental disorders, such as autism [3, 4]

  • Problems of pregnancy and the perinatal period, such as fetal malnutrition, hypoxia, infection, trauma, or prematurity

  • Hereditary abnormalities, such as inborn errors of metabolism or chromosomal aberrations

  • Medical conditions of infancy or childhood, such as central nervous system (CNS) infection or trauma, or lead poisoning

Physical causes are evident in most cases of moderate-to-profound ID. A disadvantaged environment is more likely in mild ID.

Many of the classification systems for ID have been based on the timing of the insult to the CNS. The successive classification systems developed by the American Association on Intellectual and Developmental Disabilities (AAIDD) also followed the timing approach.

Prenatal Causes - Genetic Disorders

Prenatal genetic disorders are characterized by changes in the genetic material, which may or may not have been inherited from the parents. Prenatal genetic disorders are characterized by changes in the genetic material, which may or may not have been inherited from the parents. Recent advances in the science and understanding of genetics have allowed a higher diagnostic yield from such testing. [5]

Chromosomal aberrations

Down syndrome is the best-known example of a prenatal genetic disorder. In 95% of cases, Down syndrome is caused by trisomy 21, in which the extra chromosome 21 in the egg or sperm cell results from the nondisjunction in the meiotic stage. [6] When such a gamete becomes fertilized, the fetus will have an extra chromosome 21 in all cells, for a total of 47 chromosomes.

In cases of Down syndrome caused by translocation, there are 46 chromosomes, but chromosomal material from 47 chromosomes is present because an extra chromosome 21 is attached (translocated) to another chromosome, usually chromosome 14 (designated as t(14;21)). In approximately half of translocation cases, a parent (usually the mother) has a balanced translocation, ie, 45 chromosomes with t(14;21). If a child has translocation Down syndrome, the parents should be examined for the presence of a balanced translocation. This is important in genetic counseling because when the mother or father has a t(14;21) translocation, the chance of having a child with Down syndrome is 1 in 10 if in the mother or 1 in 20 if in the father. [7, 8, 9]

In another variant, mosaicism, some cells have 47 chromosomes and others have 46 because of an error in one of the first cell divisions of the fertilized egg. The characteristic phenotype of Down syndrome is basically the same in trisomy 21 and in translocation. The main features are upward-slanted palpebral fissures, a low nasal bridge with epicanthal folds, a small mouth and ears, a single palmar crease (simian crease), a flat nasal bridge, short and wide palms, and a characteristic dermatoglyphic pattern.

A loss of part of a chromosome is called a deletion. The best-known example is cri-du-chat syndrome, which is characterized by a high-pitched voice and is caused by a deletion in chromosome 5p3. [10] Note that most fetuses with chromosomal aberrations are not viable. Approximately 40-50% of spontaneously aborted fetuses have a chromosomal anomaly. Only 2 of 10 fetuses with Down syndrome are born alive.

A new method of using DNA probes and fluorescence in situ hybridization has brought new light to many of the malformation syndromes previously classified as being of unknown origin. The same submicroscopic deletions (microdeletions) of DNA have been reported in chromosome 15q11-12 in the Prader-Willi and Angelman syndromes, despite the fact that these syndromes have different phenotypes. [11] Because of the mechanism of imprinting, the Prader-Willi syndrome results when the microdeletion is in the chromosome of paternal origin and the Angelman syndrome results when it is of maternal origin. [12]

Persons with the Prader-Willi syndrome have an excessive appetite and indiscriminate eating habits, leading to obesity. Because this syndrome has no clear pathognomonic features, it may remain undiagnosed, and such individuals might even be referred for psychiatric treatment because of an eating disorder. Obviously, psychological factors are not the primary cause here, but supportive psychotherapy might be helpful. The treatment is based on behavioral modification, the institution of strict environmental limits on food intake, and necessary educational and habilitative programming. In addition, some studies have demonstrated that treatment with growth hormone improves somatic and behavioral deficits in these patients. [13, 14, 15, 16]

Disorders with autosomal-dominant inheritance

Tuberous sclerosis is an example of the disorders in this group, which might be associated with ID. It is caused by a mutation in a gene affecting the formation of the ectodermal layer of the embryo. Because the skin and the CNS develop from this layer, abnormalities are seen in both.

The skin lesions include angiofibromas in the form of macules on the cheeks (adenoma sebaceum), with a butterfly-like distribution, especially after puberty. Café au lait spots or nonpigmented ash leaf–shaped areas are also found. ID, epilepsy, and calcifications in the brain are seen, as are tumors. Epileptic seizures often begin as infantile spasms, which should alert the physician to look for other symptoms of this disorder.

If tuberous sclerosis is diagnosed, both parents should be examined carefully because the mutation is inherited in approximately 28% of cases. Because of the dominant inheritance, the risk of recurrence is 50% for each pregnancy. The expression of this gene mutation varies from small skin discolorations (which may indicate a carrier state) to multiple disabling conditions. It is a relatively rare disorder (prevalence of 1 in 30,000 to 1 in 50,000 live births), but it may be found in approximately 0.5% of persons with severe ID. [17]

Disorders with autosomal-recessive inheritance

Most metabolic disorders belong to this category. They are caused by single mutated genes that disturb the metabolism by deficient enzyme activity. The risk of healthy carrier parents having an affected child is 25% for each pregnancy. The diagnosis is made by detection of abnormal metabolic products in the urine, blood, or tissues and/or by low or absent enzyme activity.

Phenylketonuria (PKU) is the best known and most common of the metabolic disorders, with a prevalence of approximately 1 in 10,000 live births. The enzymatic defect is diminished activity of phenylalanine hydroxylase, which leads to a high serum phenylalanine level, affecting, among other things, myelination of the CNS. It was described in 1934 by Folling in 10 children with ID, hypertonia, and hyperreflexia, with a musty odor in urine and sweat. Seizures and tremors are common, as are eczema and psychotic manifestations.

The clinical symptoms can be prevented by use of a low-phenylalanine diet soon after birth. In most developed countries, all newborns are screened for PKU. Increasingly, a lifelong low-phenylalanine diet is recommended to prevent later deterioration in cognitive functions. Women with PKU who were successfully treated do not have clinical manifestations themselves but still have phenylalanine blood levels high enough to cause brain damage to a fetus if they become pregnant. To avoid this, they should start to follow the diet again before they become pregnant.

X-linked mental retardation

Fragile X syndrome is the most common inherited form of mental retardation and, after Down syndrome, the most common genetic form. It is X linked, with dominant inheritance, and the penetrance is lower in females. Because of a constriction at the location Xq27.3, it appears as if the chromosome is fragile and a part of it is breaking off.

Prepubertal boys with this syndrome look quite normal. They often are restless and hyperactive and have a short attention span. Their developmental milestones, especially speech development, are delayed. After puberty, the characteristic phenotypical features may appear. They include an oblong face, prominent ears and jaw, and macroorchidism. Most have moderate mental retardation, but retardation is more severe in others. Male carriers do not have mental retardation. Females with fragile X syndrome who have the full mutation and are symptomatic usually have learning disabilities or mild mental retardation. Behavioral symptoms have been described in these individuals, ie, hyperactivity and social withdrawal in approximately 50% and depression in approximately 25%.

Maternal infections

Viral infections in the mother can interfere with organogenesis, and the earlier in pregnancy they occur, the more severe their effect will be, as exemplified by congenital rubella. Rubella infection during the first month of pregnancy affects the organogenesis of 50% of embryos. Infection in the third month of pregnancy still disturbs the development of 15% of fetuses. Various systems are affected, and as a result, symptoms and impairments may vary and include mental retardation, microcephaly, hearing and vision impairment, congenital heart disease, and behavior problems. Fortunately, the incidence of congenital rubella has greatly decreased because of the availability of immunization for prospective mothers.

Congenital cytomegalovirus infection may result in microcephaly, sensorineural hearing loss, and psychomotor retardation. Antibodies against cytomegalovirus are found in approximately 80% of adults. Depending on the population, primary infections occur during 2-5% of pregnancies. Cytomegalovirus inclusion bodies are seen in urine specimens of newborns who were infected prenatally.

Congenital toxoplasmosis may result in significant problems in approximately 20% of infected infants (eg, hydrocephalus, microcephaly, psychomotor retardation, vision and hearing impairment) and in milder developmental problems later in life.

Congenital human immunodeficiency virus infection has been increasing in importance. In a German study of 41 children born to mothers who were positive for human immunodeficiency virus infection, neurological symptoms were described at age 1-7 years. Human immunodeficiency virus encephalopathy was characterized by microcephaly, progressive neurological deterioration, mental retardation, cerebellar symptoms, and behavioral changes. Prophylactic intravenous immunoglobulin therapy with and without zidovudine often was able to prevent regression. Improvement was seen with zidovudine treatment.

Toxic substances

The most important of the teratogenic substances is ethanol, which is the cause of fetal alcohol syndrome (FAS). The prevalence of this syndrome varies around the world, but its occurrence in industrialized countries is estimated to be approximately 1 in 1000 newborns. When used heavily during pregnancy, alcohol causes abnormalities in 3 main categories: (1) dysmorphic features, which originate in the period of organogenesis; (2) prenatal and postnatal growth retardation, including microcephaly; and (3) CNS dysfunction, including mild-to-moderate mental retardation, delay in motor development, hyperactivity, and attention deficit. The severity of the symptoms is related to the amount of alcohol ingested.

Toxemia of pregnancy and placental insufficiency

Intrauterine growth retardation has many causes, the most important being maternal toxemia with its consequences, ending in insult to the CNS. Prematurity may be of maternal or fetal origin. When it is connected with fetal developmental deviations, the prognosis depends on the infant's general condition. Prematurity and especially intrauterine growth retardation predispose to many perinatal complications, which may result in insult to the CNS and developmental problems.

Perinatal Causes

This period refers to 1 week before birth to 4 weeks after birth.


During the neonatal period, the most important infection, from the point of view of its developmental sequelae, is herpes simplex type 2. The neonate is infected during the delivery and may develop encephalitis within 2 weeks. Early treatment with acyclovir may alleviate the otherwise poor outcome, ie, microcephaly, profound mental retardation, and neurological deficits. Neonatal bacterial infections might result in sepsis and meningitis, which, in turn, may cause hydrocephalus.

Delivery problems

During delivery, asphyxia is the most important factor causing an insult to the CNS. It leads to cell death, which might be demonstrated with neuroimaging techniques as leukomalacia. Premature infants and those with intrauterine growth retardation are at special risk for damage to the cortex or thalamus, which, in addition to affecting intelligence, causes various symptoms of cerebral palsy (CP) and seizure disorder, depending on the location of the pathological condition. Importantly, note that asphyxia alone does not cause mental retardation.

Neurologic symptoms during the neonatal period have a strong association with prenatal developmental deviations and later neurologic integrity and intellectual level. For these reasons, infants with perinatal problems need a thorough examination for dysmorphic features and close follow-up because multiple disabilities might become evident later in life.

Other perinatal problems

Retinopathy of prematurity (formerly referred to as retrolental fibroplasia) was seen frequently when the use of 100% oxygen in neonates was common, resulting in blindness. It is often associated with other CNS damage, mental retardation, and other developmental problems. Infants with extremely low birth weight are at risk for intracranial hemorrhage and hypoglycemia resulting from a lack of hepatic glycogen storage. These neonatal problems may have results similar to those of asphyxia. Hyperbilirubinemia may result from increased destruction of red cells (eg, hemolysis due to maternal-child blood group incompatibility) or decreased excretion of bilirubin (eg, due to an immaturity of liver function). The brain damage that may ensue results in manifestations of various degrees, including CP, sensorineural hearing loss, and mental retardation.

Postnatal Causes


Bacterial and viral infections of the brain during childhood may cause meningitis and encephalitis and result in permanent damage. The number of these complications has decreased because of improved treatment and the availability of immunizations such as that for measles.

Toxic substances

Lead poisoning is still an important cause of mental retardation in the United States. The most frequent source of lead is pica (ie, ingestion of flaking, old, lead-based paint). Other sources of lead are certain fruit-tree sprays, leaded gasoline, some glazed pottery, and fumes from burning automobile batteries. Gastrointestinal symptoms dominate in acute poisoning. Headache may be associated with increased intracranial pressure, which may even lead to coma. Late manifestations include developmental retardation, ataxia, seizures, and personality changes.

Other postnatal causes

Among childhood malignancies, brain tumors are second in frequency after leukemias. Of these, 70-80% are gliomas, symptoms of which depend mostly on location. Some are benign and treatable, but most have deleterious effects, resulting in various neuropsychiatric symptoms depending on their location and extent. In addition, treatment such as surgery and radiation might affect the integrity and function of the brain. Traffic accidents, drowning, and other traumas are the most common causes of death during childhood. Even greater is the number of children who become disabled. Near-drowning is often devastating, but even in these cases, improvement of functional capacity may be achieved by rehabilitation because the developing brain has the ability to recover.

Psychosocial problems

The developmental level of a growing individual depends on the integrity of the CNS and on environmental and psychological factors. The importance of environmental stimulation for child development has been appreciated since research on children in institutions showed that development was severely affected in a depriving environment, even if adequate physical care was provided. Poverty predisposes the child to many developmental risks, such as teenage pregnancies, malnutrition, abuse, poor medical care, and deprivation.

Severe maternal mental illness is another risk factor. Mothers with severe and chronic illness might have difficulty providing adequate care and stimulation. Maternal depression during pregnancy and postpartum has been shown to be associated with developmental delay in children at 18 months of age. [18]

Children of mothers who have schizophrenia are at risk for the development of cognitive deficits, although these may not be secondary to maternal illness but may represent a genetically determined predisposition to schizophrenia. Psychotic illness in a child has been shown to be associated with a decline in cognitive abilities.

Unknown causes

Despite detailed assessment, no cause can be identified in approximately 30% of cases of severe mental retardation and in 50% of cases of mild mental retardation. This, of course, reflects the inadequacy of diagnostic techniques, rather than a lack of causation.


Why Should Psychiatrists Learn About Intellectual Disability?

Mental retardation affects approximately 1-3% of the population in developed countries. Until recently, a significant proportion of individuals with mental retardation were cared for in residential facilities such as state-run training schools. The recent trend has been to move individuals who are mentally disabled out of institutional settings and into more community-based living arrangements such as group homes. This trend underscores the idea that mental retardation cannot be categorized as a mental illness in the strictest sense of the term. Thus, these individuals should be viewed as merely a population requiring more-than-average help in the daily chores of living.

Of individuals with mental retardation, an estimated 40-70% have diagnosable psychiatric disorders. These individuals are not the only ones who have contact with psychiatrists.

Like anyone else, a person who is developmentally disabled may exhibit emotional, behavioral, interpersonal, or adjustment problems that do not constitute major psychiatric disorders but that, nonetheless, may benefit from psychiatric input.

Sampling issues probably account for the wide variety in prevalence rates. For example, studies differ as to whether subjects are selected randomly or referred specifically to psychiatric clinics, and studies also may assess different mental disorders.

Einfeld and Tonge used the Developmental Behavior Checklist, a 96-item checklist that helps to detect the presence of emotional and behavioral problems. Rated behaviors fall into 6 subscales, as follows: (1) disruptive, (2) self-absorbed, (3) communication disturbance, (4) anxiety, (5) autistic relating, and (6) antisocial. Based on their population sample of all of the children and adolescents (aged 4-18 y) in 5 regions of New South Wales, Australia, 40.7% of those with an IQ below 70 could be classified as having severe emotional or behavioral disorders. Perhaps more worrisome is the fact that less than one tenth of these children and adolescents with major psychiatric illness received specialized psychiatric care. [19]

In the United States, the same phenomenon holds true; the psychiatric needs of persons of all ages with intellectual disability are largely unmet. Approximately 1.5 million persons aged 5-65 years received services for mental retardation in the United States. [20]

Assuming that at least 40% of these individuals have emotional or behavioral problems, approximately 600,000 people can benefit from psychiatric care. Unlike in the past, because most people with mental retardation are no longer living in institutions, psychiatrists have an important role in enhancing the patients’ quality of life in the community, thereby reducing the need for multiple institutionalizations.


Emergency Evaluation and Treatment

Evaluation and treatment of psychiatric emergencies in individuals who are intellectually developmentally disabled pose additional challenges. The goal of crisis intervention is the same as in the general population (ie, to reduce the risk of harm to self/others and to accomplish this objective in the least restrictive setting). For optimum results, the assessment and treatment of patients who are intellectually disabled should include the input of the primary caregivers.

Psychiatrists who are unaccustomed to the usual presentation of ID may be nonplussed by the clinical manifestations of psychiatric emergencies in these patients. Limitations in cognition and verbal expression make it difficult for patients to describe abstract concepts such as mood, guilt, and ideas of reference.

Sovner identified 4 aspects of ID that may influence diagnosis, as follows: [21]

  • Intellectual distortion: Emotional symptoms are difficult to elicit because of deficits in abstract thinking and in receptive and expressive language skills.

  • Psychosocial masking: Limited social experiences can influence the content of psychiatric symptoms (eg, mania presenting as a belief that one can drive a car).

  • Cognitive disintegration: A decreased ability to tolerate stress can lead to anxiety-induced decompensation (sometimes misinterpreted as psychosis).

  • Baseline exaggeration: Severity or frequency of chronic maladaptive behaviors can increase after the onset of psychiatric illness.

To reduce distraction or overstimulation, evaluations of the patient are best performed in a safe quiet area, away from the prying eyes and ears of other staff and patients. Care providers should be included in the assessment process because they can be a calming influence on the patient and they can provide valuable information.

Taking a biopsychosocial approach to problem solving should lead to interventions that address biological, psychological, and social factors that caused the crisis situation. While resolving every aspect of the crisis is not necessary, identifying and addressing the main concerns of the caregivers is important. Once the immediate crisis is resolved, the remaining problems can be referred to community or state agencies.

Lowry and Sovner describe 4 functions of problem behavior that should be considered in any evaluation, as follows: [22]

  • Socioenvironmental control: Aggression and self-injurious behavior can be reinforced (ie, removing a person from an unpleasant situation in response to such behavior will increase the probability that the person will react similarly in the future).

  • Communication: Problem behaviors can be a nonverbal means of communicating a variety of messages (eg, attention, discomfort, needs).

  • Modulation of physical discomfort: Medical conditions, including adverse effects of medications, can cause physical discomfort, leading to aggression or self-injurious behavior.

  • Modulation of emotional discomfort: Problem behaviors can occur as a state-dependent function of disorders such as major depression or bipolar disorder, manic phase.

Emergency evaluation should include a thorough physical examination, including appropriate laboratory studies such as electrolytes, blood count, ECG, drug levels, and sometimes CT scans or MRI and electroencephalogram. Psychiatric assessment, consisting of history from the patient and caregivers and a mental status examination, helps establish a correct diagnosis. When possible, treatment should be directed at the medical illness, psychiatric disorder, or other underlying cause of the maladaptive behavior. Symptomatic treatment of aggressive behavior is often necessary and helpful when a clear-cut medical or psychiatric diagnosis cannot be established.

Based on the emergency evaluation, any of the following dispositions may be agreed upon:

  • Return to current living situation

  • Respite care or increased monitoring at home

  • Medical treatment

  • Inpatient psychiatric hospitalization

Changes in the legal, institutional, and financial structure of psychiatric care have set a higher threshold for inpatient hospitalization. As in the general population, hospitalization clearly is indicated when a person poses an imminent danger to themselves or to others because of a psychiatric illness. Hospitalization also may be indicated when outpatient treatment has been unsuccessful in halting a psychiatric decompensation or when a psychiatric illness has progressed to the point that the person no longer is able to function adequately in the community.

Obtaining hospitalization for extended medication trials or for initial monitoring of a new course of pharmacologic treatment is becoming increasingly difficult, despite the fact that hospitalization may be appropriate in some of these situations. Finally, Sovner and Hurley make clear the opinion that inpatient staff should not be expected to assume responsibility for the treatment of long-standing maladaptive behavior. They support discharging the patient from the hospital as soon as the crisis has resolved. [23]

Case example

A 38-year-old man with a history of impulse control disorder, moderate ID, and obsessive-compulsive disorder was brought to the emergency department by police, accompanied by his care provider. He was being managed on as an outpatient on sertraline and carbamazepine. His behavior was reported to have abruptly changed. He had returned to his group home from his day program and went straight up to his room and pulled all his clothes out of the closet. He then proceeded to fold them and put them away, only to pull them all out and start folding again. When staff tried to persuade him to come down for dinner, he became agitated and picked up a chair. When the staff backed off, he proceeded to bang his head on the wall. At this point, police were summoned and the patient was transported to the ED.

The ED physician stated that the patient had been uncooperative initially and when he was given a lorazepam injection he calmed down enough to be medically cleared. When approached by the psychiatrist, he was seen to be quietly rocking back and forth. He avoided eye contact and did not respond to questions. The care provider informed the ED physicians that the patient liked soft drinks. He was offered some and warily accepted it. After that he became somewhat responsive to questions and said “I don’t like Joe.” The care provider explained that Joe was his new roommate. He had heard reports that Joe was teasing the patient on the bus and on occasion helped himself to the patient’s personal items. After private discussion, the care provider informed the patient that he would have a different roommate, one whom the patient liked. At this, the patient smiled and visibly relaxed and asked if he could go home and have dinner.


Outpatient Psychiatric Care

Approach Considerations

The current trend toward deinstitutionalization in the care and management of individuals who are intellectually disabled predicts that the majority of patients will live in a community setting with a good deal of assistance. Adequate management of their psychiatric problems is essential to prevent institutionalization and to enhance their quality of life as full participants in society.

Psychiatrists play a key role in the long-term outpatient care of mental illness in people with developmental disability. Ideally, the team of caregivers should include a psychiatrist, primary care physician, psychologist, social worker, nurse clinician, case manager, occupational therapist, vocational counselor, home provider, and family member who work together to ensure the best outcome. While all these individuals may not be located in one place, their input should be sought and coordinated by the case manager when developing a comprehensive treatment plan.

Use of psychotropic medications to treat behavioral problems of patients who are developmentally disabled often has been controversial. Even clinicians who are convinced of the beneficial effects of certain psychotropic medications in the treatment of persons who are mentally disabled prefer to use such agents only when a specific DSM-5 diagnosis is present. While this would be the perfect ideal for which to strive, it may not always be feasible.

When a DSM-5- oriented diagnostic approach yields no more than a relatively nonspecific diagnosis (eg, impulse control disorder not otherwise specified [NOS]), particularly in those with more severe intellectual disability, clinicians may have to focus on abnormal behavioral symptoms as indications for choosing psychotropic medications. These problems include self-injurious behavior, physical aggression, impulsivity/hyperactivity, suicidal ideation/behavior, sexually aggressive behavior, sexual self-exposure/public masturbation, social withdrawal, excessive dependence, noncompliance/oppositional behavior, and self-induced vomiting.

Assessment of Mental Illness in Persons With Intellectual Disability

The psychiatric diagnostic evaluation of persons with ID is, in principle, the same as for persons who do not have ID. The diagnostic approaches are modified, depending on the patient's cognitive level and, especially, communication skills. For persons who have mild ID and good verbal skills, the approach does not differ much from diagnosing persons with average cognitive skills. The poorer the communication skills, the more one has to depend on information provided by caregivers familiar with the patient and on direct behavioral observations. The assessment includes the following components.

Comprehensive history

The history taken from the patient and from several caregivers in different settings covers the following:

  • Presenting symptoms, including concrete descriptions of specific behaviors in various situations and settings, their change over time, antecedent events, and the way the various caregivers handle the behaviors

  • Psychiatric review of systems, including premorbid and current behavioral and personality patterns, adaptive functioning, self-care, communication, and social functioning

  • Details of previous psychiatric treatment, with particular emphasis on adverse effects of medications that could cause the presenting symptoms

  • Past and present educational and habilitative interventions, work programs, and living situations, including their quality, consistency, and appropriateness; the availability of supportive services; and the long-term plans for the patient's care

  • Parents'/caregivers' attitudes toward the patient, their understanding of the patient's disability, and support for growth versus overprotection

  • Review of past cognitive tests and evaluations or request for new ones if needed

Patient interview

Ample time must be allotted for the patient interview, which typically takes longer than for patients without ID. Sufficient time is needed to put the patient at ease. The verbal examination should be adapted to the patient's communication skills and should use clear and concrete language, structure, reassurance, and support. Leading questions and questions requiring yes or no answers should be avoided, and the interviewer should ensure that questions are understood.

Patients with sensory impairments such as blindness or deafness must be approached in a manner that recognizes their needs through the use of appropriate interpreters or communication devices.

Mental status may be assessed in the context of conversation, rather than in a formal examination. Starting the interview with a discussion of a patient's strengths and interests, rather than problems, often is helpful. Later, focus on the patient's understanding of disability, limitations, and reasons for the referral. Nonverbal aspects of the interview include observations of performance on selected tasks, relatedness, expression of affect, impulse control, attention span, activity level, and the presence of unusual behaviors or seizures.

Medical review

This review should include developmental and medical history, past etiological assessments, and coexisting general medical disorders and their treatments. The latter is particularly important because undiagnosed medical conditions are frequent in this population and may lead to behavioral symptoms.

Diagnostic formulation

Data from the assessments should be interpreted in light of developmental level, communication skills, associated handicaps, life experiences, education, and family and sociocultural factors. A particular behavior may suggest an underlying mental disorder if it is part of a pattern of a defined mental disorder syndrome. The possibility of sexual or other abuse that the patient cannot report should be considered. A DSM-5 diagnosis (in addition to ID) should be made if the appropriate criteria are met. The diagnostic statement should include a description of the person's strengths, deficiencies, and needs, including intellectual, adaptive behavior, communication, health, and psychosocial domains. A comprehensive assessment should yield a multiaxial diagnostic formulation with appropriate differential, and supporting evidence for diagnoses should be highlighted.

Specific Diagnosis of Common Comorbid Mental Disorders

Pervasive developmental disorders

Most children with pervasive developmental disorders also have ID. However, children with ID alone do not have significant impairments in reciprocal social interaction and can engage in social communication, verbal or nonverbal (such as gestures and eye contact), appropriate to their developmental level.

Attention deficit hyperactivity disorder

The diagnostic criteria for attention deficit hyperactivity disorder (ADHD) are based on observable behavior as reported by multiple informants and thus can be applied to nonverbal children. ADHD should be differentiated from situation-specific inattentiveness, such as at school if the academic expectations are too high, and adverse medication effects. In assessing noncompliance (ie, not following commands of caregivers), one should consider the child's ability to understand social rules and the presence of sufficient skills to communicate opposition.

Tic disorders and stereotypic movement disorder

In Tourette disorder, the movements, as opposed to self-stimulatory stereotypies seen in persons with severe ID, are less complex and appear involuntary. For the latter, the diagnosis of stereotypic movement disorder may be used if other mental disorders are excluded. The specifier "with self-injurious behavior" is added if bodily damage results. Self-injurious behavior is common in certain ID syndromes, especially Lesch-Nyhan syndrome.

Mental disorders due to a general medical condition

Intellectual disability, in and of itself, does not constitute a medical condition to which aberrant behavior or emotional disturbance should be ascribed. The attribution of behavioral or emotional disturbance to a general medical condition should be used only when evidence from the history, physical examination, or laboratory findings indicates that the disturbance is a direct consequence of a specific medical condition. For example, in the case of Down syndrome, hypothyroidism may present as symptoms of depression. In such cases, the medical disorder to which the depression should be attributed is hypothyroidism, not Down syndrome.

Schizophrenia and other psychotic disorders

Schizophrenia can be diagnosed in the usual manner in verbal persons with mild ID but rarely, if at all, in persons with more severe retardation. For the latter, the less specific diagnosis of psychotic disorder NOS may be made if behavioral features such as grossly disorganized behavior and negative signs are present but were absent in the premorbid period. Conversation with an imaginary friend should not be confused with hallucinations.

For related information, see Medscape's Schizophrenia Resource Center.

Mood disorders

Mood disorders, especially depressive disorders, are quite common in persons with ID. In verbal persons with mild ID, the complaints are simple and concrete. History obtained from caregivers and evidence of neurovegetative signs help in assessing the mood change. Depression also may manifest as aggressive behavior. Environmental events, such as a precipitous move to a new setting or change in care provider, may trigger a depressive episode. Adverse effects of medications should be considered, for example, depression resulting from beta-blockers or agitation associated with akathisia from a neuroleptic drug.

For related information, see Medscape's Depression Resource Center.

Anxiety disorders

Verbal persons with mild ID can report on subjective feelings of anxiety. In nonverbal persons, symptoms such as avoidance behaviors and agitation might suggest the diagnosis. The tendency toward anxiety and social avoidance also is a part of the behavioral phenotype of fragile X syndrome.

For related information, see Medscape's Anxiety Disorders Resource Center.

Posttraumatic stress disorder

Posttraumatic stress disorder in persons with ID might be quite frequent and should be routinely considered in the differential diagnosis. These individuals are vulnerable to abuse because of difficulties in reporting it and a tendency to want to please others.

Obsessive-compulsive disorder

The diagnosis of obsessive-compulsive disorder (OCD) may be difficult in nonverbal persons who cannot report on obsessional thoughts underlying their compulsions. Some repetitive behaviors, for example, hoarding objects, flicking lights on and off, and tidying and arranging, all have been suggested as indications of OCD in persons with ID. Self-restraint, for example, insistence upon wearing a helmet or other protective device, is a behavior that has been described in persons who also exhibit self-injurious behavior and might suggest the ego-dystonic nature of self-injury. A connection between some self-injurious behaviors and OCD has thus been postulated.

Eating disorders

Anorexia and bulimia nervosa are relatively rare in the context of ID, particularly moderate to severe ID, but ID is a predisposing factor for other eating disorders such as pica and rumination. The ingestion of nonnutritive substances, pica, and the regurgitation and rechewing of food, rumination, occur with greater frequency as the severity of cognitive disability increases. When these behaviors are a focus of clinical attention, the diagnoses should be considered.

For related information, see Medscape's Eating Disorders Resource Center.


Treatment Planning and Stressors That May Trigger Problems

Table 1, which appears in the Expert Consensus Guidelines series, "Treatment of Psychiatric and Behavioral Problems in Mental Retardation," lists stressors that may trigger problems in individuals who are mentally retarded. A complete evaluation and an individualized treatment plan require attention to the possible short-term and long-term stressors that may be triggering or exacerbating psychiatric disorders or behavioral problems in persons with mental retardation.

Although none of the stressors listed in Table 1 is specific to individuals with mental retardation, each is more likely to occur and cause difficulties in those whose coping skills already are compromised substantially. Helping the individual, family, and caregivers deal with or eliminate stressors sometimes may be the primary target of treatment, and this often opens the door to a realization of other treatments that may be necessary.

Table 1. Stressors That May Trigger Behavioral Problems (Open Table in a new window)

Types of Stressor


Transitional phases

Change of residence, new school or work place, altered route to work

Development landmarks (eg, going into puberty, achieving majority)

Interpersonal loss or rejection

Loss of parent, caregiver, friend, roommate

Breakup of romantic attachment

Being fired from a job or suspended from school


Overcrowding, excessive noise, disorganization

Lack of satisfactory stimulation

Reduced privacy in congregate housing

School or work stress

Parenting and social support problems

Lack of support from family, friends, or partner

Destabilizing visits, phone calls, or letters



Physical or sexual abuse

Illness or disability

Chronic medical or psychiatric illness

Serious acute illness

Sensory defects

Difficulty with ambulation


Stigmatization because of physical or intellectual problems

Taunts, teasing, exclusion, being bullied or exploited


Due to inability to communicate needs and wishes

Due to lack of choices about residence, work situation, diet

Because of realization of deficits

With increasing severity of mental retardation, the incidence of concomitant sensory and motor deficits increases. A greater degree of mental retardation suggests a greater amount of brain damage, reflected in a higher occurrence of impaired vision, hearing, and speech and communication and a higher occurrence of seizure disorders. Substance abuse is not unheard of among patients who are mentally retarded. A comprehensive treatment plan should include interventions to address these problems.


Psychosocial Treatment Modalities

Multidisciplinary treatment teams use a variety of psychosocial modalities to address behavioral problems experienced by patients who are mentally retarded. The 3 behavioral interventions recommended by the expert consensus panel for most situations are as follows:

Applied behavior analysis includes techniques that are based on the principles and methods of behavior analysis and are intended to build appropriate functional skills and reduce problem behavior. These include the following:

  • Behavior-accelerating procedures, such as contingent reward for specific behaviors that are incompatible with problem behavior

  • Behavior-decelerating techniques, such as contingent reward for specified time periods, during which the problem behavior did not occur; extinction; overcorrection; response cost; time-out; contingent restraint

  • Behavioral parent and teacher/staff training to help them function as cotherapists and/or to avoid incidental reinforcement of the problem behavior

Managing the environment includes reducing problem behaviors by rearranging physical and/or social conditions that seem to provoke them; examples include changes in activities (eg, noise, temperature, lighting, crowding) and/or enrichment of environment through social or sensory stimulation.

Client and/or family education includes helping clients and/or families understand more about the behavioral psychiatric problems that may accompany mental retardation and how to manage them.

Local sources of information

Depending on the state, clinicians and families can obtain information on local services, other resources, and entitlement to services from the state department of mental retardation, the state department of public health, or the state department of education.

University-affiliated programs for persons with developmental disabilities

These programs, located in all states, focus on providing clinical services, training professionals, and performing research related to developmental disabilities. Clinicians might refer patients to such programs and/or use them as sources of information about services in their areas. The addresses and details about the university-affiliated programs may be obtained from the following organization:

Association of University Centers on Disabilities

1010 Wayne Ave, Suite 920

Silver Spring, MD 20910 USA

(301) 588-8252

National organization for persons with developmental disabilities

The national organizations concerned with services for persons with developmental disabilities and their families can provide addresses of the local chapters, which might be a good source of information concerning local services. Some of these organizations include the following:

ARC (formerly Association for Retarded Citizens)

1010 Wayne Avenue, Suite 650

Silver Spring, MD 20910 USA

(800) 433-5255

Autism Society of America

7910 Woodmont Avenue, Suite 300

Bethesda, MD 20814-3067 USA

(800) 3AUTISM

National Down Syndrome Congress

1370 Center Drive, Suite 102

Atlanta, GA 30338 USA

(800) 232-NDSC

Williams Syndrome Association

PO Box 297

Clawson, MI 48017-0297 USA

(800) 806-1871

National Fragile X Foundation

PO Box 37

Walnut Creek, CA 94597 USA

(800) 688-8765


Psychopharmacological Treatment

In many individuals with mental retardation, behavioral problems respond to psychosocial interventions. However, situations exist in which psychotropic medications can enhance a patient's response to psychosocial treatment. Other clinical conditions require psychopharmacologic treatment at the outset.

Psychiatrists are well aware of the psychopharmacologic management of various mental illnesses that meet DSM-IV-TR diagnostic criteria. A number of excellent textbooks, review articles, and practice guidelines are available on this topic, and detailing these is beyond the scope of this article.

The literature often is limited or contradictory regarding the use of medications in the management of behavioral problems in patients who are mentally retarded and who do not meet criteria for DSM-IV-TR diagnosis. Therefore, this section draws from the Expert Consensus Guidelines series, "Treatment of Psychiatric and Behavioral Problems in Mental Retardation." These guidelines are based on surveys of 48 experts on psychosocial treatments and 45 experts on medication treatment of mental retardation. These recommendations do not replace clinical judgment, which must be tailored to the particular needs of each patient.

The US Health Care Financing Administration recognizes that the use of medications sometimes is the least intrusive and most positive intervention, but it does not specify the circumstances when medication is an appropriate part of the initial treatment plan. The combined ratings of the psychosocial and medication experts agree that medication definitely is indicated from the outset for patients with psychotic, bipolar, and major depressive disorders; medication may be indicated for a number of other DSM-IV-TR disorders.

There is less general enthusiasm for the use of medications at the very onset of symptoms that are not part of a DSM-IV-TR disorder, and the 2 groups of experts disagree on this issue. The medication experts are somewhat more likely to recommend the use of medications at the beginning of treatment for several target symptoms, even when no specific DSM-IV-TR diagnosis can be made. Table 2 lists clinical situations in which including medications in the initial treatment plan is beneficial.

Table 2. When to Include a Medication in the Initial Treatment Plan (Open Table in a new window)

Clinical situation

Condition in which medication is recommended as part of initial treatment

Condition in which medications should be considered as part of initial treatment

DSM-IV-TR disorders


Bipolar disorder, manic phase

Bipolar disorder, depressed phase

Major depressive disorder

Psychotic disorder NOS*


Mood disorder NOS

Panic disorder**


Stereotypic movement disorder with

self-injurious behavior**

Target symptoms in

the absence of specific

DSM-IV-TR disorder

Suicidal ideation/behavior*

Self-injurious behavior**

Interpersonal aggressive behavior**


Factors that suggest the

need for medication as

part of the initial

treatment plan

History of behavioral deterioration when off medication

Self-injurious behavior with risk of

lasting harm*

Aggression to others that poses a

physical risk*

Very severe symptoms*

Previous good response to medications*

Lack of response to psychosocial


Symptoms that interfere significantly

with individual's ability to participate in


Family history of good response to a

psychiatric medicine**

Symptoms that have persisted for more

than a few weeks**

Symptoms that are very disruptive to

family or staff**


*Rated first-line by the medication experts and second-line by the psychosocial experts

**Rated higher second-line by the medication experts only



Experts were asked about the choice of medications when behavioral symptoms are present in a patient for whom a DSM-IV-TR diagnosis cannot be made and the symptoms (1) have not responded adequately to appropriate behavioral and environmental interventions and (2) remain severe and persistent enough that medication treatment definitely is indicated. The recommendations of the experts are summarized in Table 3.

Table 3. Selection of Medications for Target Symptoms (Open Table in a new window)


Preferred Medications

Self-injurious behavior

Newer atypical antipsychotic

Anticonvulsant/mood stabilizer

Also consider selective serotonin reuptake inhibitor (SSRI) **

Physical aggression to people or


Newer atypical antipsychotic

Anticonvulsant/mood stabilizer

Also consider SSRI

Nonaggressive agitation

Anticonvulsant/mood stabilizer

Also consider newer atypical antipsychotic, SSRI

Suicidal ideation/behavior


Also consider anticonvulsant/mood stabilizer




Also consider benzodiazepine



Also consider alpha2-agonist, anticonvulsant/mood




Also consider zolpidem

Psychiatric or behavioral problems

in a client/patient with comorbid


Divalproex/valproic acid


Also consider gabapentin


*Recommendations to consider in italics were rated high second-line.

**Just short of first-line


Clozapine is an atypical or second-generation antipsychotic medication that has been well accepted for the treatment of patients with schizophrenia who fail to respond to all other antipsychotic medications. Clozapine was not mentioned in the Expert Consensus Guidelines, as at the time the guidelines were written, not much data existed on its usefulness in mentally retarded individuals.

More recently, a growing body of literature has been suggesting the usefulness of clozapine in treating developmentally disabled patients who do not respond to conventional medications and behavioral interventions.

Because clozapine exposes patients to potential risks, such as agranulocytosis, myocarditis, cardiomyopathy, seizures, and metabolic complications, psychiatrists have been reluctant to prescribe it to patients with mental retardation, especially in the absence of treatment guidelines in the literature. Fortunately, such a guideline is now available. [24]

By and large, a dose of 300-600 mg seems to be useful for patients when a minimum clozapine blood level of 350 ng/mL is attained. The guideline recommends strategies for using clozapine in developmentally disabled individuals with treatment-resistant cases of schizophrenia, self-injurious behavior, aggressive/destructive behavior in the absence of psychotic symptoms, abnormal involuntary movements, or polydipsia.

Common side effects include weight gain, orthostatic hypotension, tachycardia, fever, sedation, constipation, hypersalivation, and myoclonic jerks. Significant drug interactions such as the following and other issues are discussed at length in the guidelines:

  • Phenobarbital, primidone, and phenytoin can induce clozapine metabolism.

  • Tricyclic antidepressants elevate clozapine level and cardiovascular risk by prolonging QTc interval.

  • SSRI antidepressants such as fluvoxamine, sertraline, and fluoxetine increase clozapine levels.

  • Carbamazepine and oxcarbazepine might increase the risk of agranulocytosis.

  • Benzodiazepines during the early weeks of clozapine therapy might cause respiratory arrest.

In spite of these drawbacks, clozapine can be a valuable addition to the psychopharmacological choices when confronted with a patient whose behavioral problems do not respond to conventional medications and behavioral interventions.


The United States Food and Drug Administration (FDA) has approved the use of risperidone for the treatment of irritability in children with autism aged 5-16 years. Until recently, psychopharmacologic management of behavioral problems associated with mental retardation were subdivided into 2 broad, but often overlapping, categories. The first and oldest approach is to use medications for symptom control (eg, sedatives for insomnia, tranquilizers for agitation). The second approach is to carefully evaluate patients for comorbid psychiatric conditions and use specific medications to treat the psychiatric diagnosis or presumed diagnosis.

As discussed above, progress has been made by treating diagnosable psychiatric conditions that meet DSM-IV-TR criteria or at least approximate those conditions with medications appropriate for the given diagnosis. Underlying this approach was the assumption that behavioral disturbances associated with mental retardation were developmentally fixed traits and therefore could not be fundamentally altered. But recent studies have opened new avenues of clinical research and treatment of behavioral symptoms of developmental disorders.

Two multicenter, 8-week, double-blind, placebo-controlled trials of risperidone demonstrated its efficacy in the treatment of irritability associated with autistic disorder in children and adolescents, 5-16 years of age. Efficacy was assessed using the Irritability subscale of the Aberrant Behavior Checklist (ABC-I). In the first study, 101 children (mean age 8.8) and in the second, 79 children aged 5-12 years were randomly treated with risperidone or placebo. Significant improvement of ABC-I scores were noted on risperidone in both studies. Based on these findings, the FDA approved the use of risperidone for the treatment of irritability in children with autism aged 5-16 years. [25, 26, 27]

DSM-IV-TR diagnostic criteria for autism include 3 core symptom domains: (1) qualitative impairment in social interaction; (2) qualitative impairments in communication and (3) restricted repetitive and stereotyped patterns of behavior, interests, and activities. Further analysis to determine whether risperidone improves the core symptoms of autism showed significant improvements in the restricted, repetitive, and stereotypic patterns of behavior of autistic children but did not improve their social interactions and communications. The fact that one core symptom domain responds to pharmacologic treatment opens the possibility that future studies would identify effective treatments for the other core symptoms.

Integrating psychosocial and psychopharmacologic approaches to treatment planning

Treatment teams in long-term institutions have developed a variety of interventions for managing behavioral problems of mentally retarded people. These have ranged in complexity from simple one-step plans to multiple-step strategies. Positive reinforcement by rewarding desired behaviors or negative reinforcement by ignoring unwanted behaviors are often effective when applied consistently. More challenging problem behaviors require gathering detailed information, data analysis by experienced behavioral specialists, and implementing sophisticated strategies by trained treatment team members.

Ethical, social, legal, and regulatory barriers to medicating developmentally disabled individuals resulted in the growth of a whole field of behavioral management. Results of well-controlled research studies document these strategies in peer-reviewed journals. For the same reasons, psychopharmacological approaches to treating behavioral problems of mentally retarded patients have been mostly on a trial and error basis.

As more and more mentally retarded people are discharged from large institutions to live in the community, a tendency exists to rely more on medications and less on behavioral interventions. This is caused in part by the lack of experienced behaviorists in community settings. Further aggravating this problem, many group home providers have limited training and experience in systematically implementing behavior management plans.

Nevertheless, it is very beneficial to the patient if the psychiatrist, who is often the treatment team leader, is able to integrate psychopharmacological interventions with behavioral approaches. At times, this might require consulting behavioral specialists who might not be at a particular clinic. At other times, it might require guiding the care providers in the rudiments of behavioral management.

Psychopharmacological approaches and behavioral modalities can work independently or interact in beneficial or detrimental ways. As this topic is beyond the scope of this article, interested readers are referred to a publication by Sevin et al. [28]


Case Management and Record Keeping

Effective communication between treatment team members over a prolonged period of time is essential for the best outcome. A sample clinical encounter form is included below in Table 4. This form is to be used as a worksheet and should not replace usual documentation (eg, progress notes). Rather, it should be used to highlight clinical information of immediate importance. Having the worksheet in 2 parts is best.

The top portion should contain clinically useful data that are not likely to change often as the patient returns for follow-up visits. Ideally, this form should be saved as a word processor file in a personal computer so that it can be printed out for use during each visit. Team members should make brief notations in the lower section to alert others on the team regarding pressing issues and plans. The form also serves as a brief note until more complete notes are written.

Table 4. Sample Clinical Encounter Form (Open Table in a new window)

Name: John Doe

Housing: Group Home

DOB: 01/01/1960

Telephone: 555-1234

Case Manager: Mr. Johnson

Relative: Mrs. Doe (Mother) 555-4321

Home Provider: Mrs. Jane Smith

Physical Deficits: Hearing impaired; needs wheel chair

Communication: Understands English when spoken slowly; speaks only a few words

Activities of Daily Living: Seizure disorder; cerebral palsy

Cognitive Deficit: Moderate mental retardation

Aggravating Factors: Change in routine; abdominal pain; when relatives fail to visit

Medical Problems: Seizures disorder; cerebral palsy

Psychiatric Problems: Depression; 2 psychiatric hospitalizations; 3 suicide attempts

Ameliorating Factors: Supported employment; weekends with family; swimming

Date:________ Current Problems:

Mental Status:



__Poor hygiene

__Poor eye contact



















__Loose associations

__Flight of ideas



__Suicidal ideas

__Self-injurious behavior

__Homicidal ideas

__Verbally aggressive



__Hallucinations - Auditory, visual, tactile, olfactory

__Intact recent memory

__Impaired recent memory

__Impaired judgment






Patient and Family Education

Patient and family education and support can be found at the following Web sites.