Intellectual Developmental Disorder (IDD)

Intellectual Developmental Disorder (IDD), also called Intellectual Disability, is a condition that starts early in life and usually stays with children as they grow up. It might be noticed when a child has trouble reaching important growth steps expected for their age. However, it is often officially diagnosed when the child is older than 5 years, as tests like intelligence tests and adaptive functioning scales give more accurate results.

Children with IDD have problems with general thinking skills that can vary in severity. They have trouble with reasoning, planning, judgment, abstract thinking, and learning different things. They often find school hard and may also have issues with friends and everyday tasks like bathing or getting dressed. They might seem to misbehave or even hurt themselves, but the real issue is that they often do not know what behavior is right or how to express their needs at certain times.

Children who have trouble reaching intellectual growth steps but are too young or unable to take standard tests to measure their thinking skills may be diagnosed with a condition called Global Developmental Delay. Only children under 5 years old can be diagnosed this way.

What are the symptoms of Intellectual Developmental Disorder?

The symptoms of IDD include problems with thinking, understanding abstract ideas, making friends, and handling everyday tasks that help us be independent. These issues show up early in a child’s life, and severity depends on how serious the disorder is. Specific symptoms may include:

Core Symptoms:

– Intellectual problems including:

– Reasoning (e.g., understanding assumptions and consequences, and making inferences)

– Problem solving

– Planning

– Abstract thinking (e.g., understanding concepts and ideas)

– Judgment (e.g., telling right from wrong)

– Academics

– Learning

– Additional problems that lead to not meeting growth and social markers for independence and responsibility, including:

– Daily life skills (e.g., communicating, socializing)

– Gaining personal independence

Associated Symptoms:

– Not reaching milestones like crawling, walking, or talking, or doing them later than other kids

– Having a hard time remembering things, solving problems, or learning and using new information

– Struggling in school

– Difficulty talking to others, reading body language, and understanding social cues

– Having trouble making and keeping friends

– Having trouble doing daily tasks, like basic self-care (e.g., getting dressed, using the bathroom), household chores, or handling money

– Having trouble connecting learned ideas to new problems

How is Intellectual Developmental Disorder diagnosed?

IDD is diagnosed by a team of experts, like child-adolescent psychiatrists, developmental pediatricians, neurologists, and/or geneticists, working with the family. If a caregiver is worried about a child’s growth, a child-adolescent psychiatrist will use an intelligence test to find out the child’s thinking skills, or intelligence quotient (IQ), a standard measure that shows the child’s knowledge and reasoning ability. Children who score lower than two standard deviations below the average are found to have very low thinking skills that are common in children with IDD. The most common tests are the Weschler tests, where scores below 70 may show that a child has IDD. The psychiatrist, along with other experts, will confirm this diagnosis by learning more about the child through interviews with caregivers and by giving other tests and interviews to measure the child’s skills in other areas.

IDD can be mild, moderate, severe, or profound. Although IQ tests give some clues about the severity of the disorder, the doctor is better at considering different parts of general thinking skills, along with social and practical skills, to decide how severe the disorder is. This combined evaluation of the child’s intelligence score and their adaptive functioning is key in finding both the presence and the severity level of the diagnosis.

When giving tests and checking for IDD, it is important to remember that cultural factors might affect the test scores. Tests need to be adapted to each culture to be valid for measuring intelligence, and they are often not validated in underserved or minority groups. Some intelligence tests can be given to a child as early as 2.5 years old.

Severity Levels for Intellectual Developmental Disorder (Table)

Conceptual Problems

Mild

– Difficulties may not be obvious in preschool children, but school-age children show academic challenges needing help in areas like reading, writing, math, time, and money.

Moderate

– In preschool children, there are delays in language and early learning skills. School-age children have very limited academic progress compared to peers.

Severe

– The child has little understanding of language or ideas like numbers, quantity, time, or money, and needs a lot of caregiver help.

Profound

– The child will struggle with using numbers, letters, or symbols for learning or talking, but may match objects by looks and use some objects for specific purposes (e.g., a brush for hair). Motor or sensory problems may stop the child from using objects properly.

Social Problems

Mild

– The child may have immature language and communication, as well as trouble with emotions, behavior, and social situations compared to peers. There is a risk of being tricked by others, including peers.

Moderate

– The child’s language and communication skills are noticeably limited compared to peers, but they will have relationships with family and friends.

Severe

– The child’s spoken language is very limited, often using only single words, common phrases, and gestures, focused on the present. Relationships are possible with family and caregivers, and these relationships can bring happiness.

Profound

– The child has a very limited understanding of spoken language for communication, and expresses thoughts and wants mostly through gestures or other nonverbal ways. The child may understand simple, one-step instructions or gestures. Relationships with familiar caregivers are enjoyed, but motor or sensory problems may stop social activities.

Practical Problems

Mild

– The child may be able to do some self-care activities (e.g., eating, dressing, using the toilet, brushing teeth, washing hands), but may need more help with more complex daily tasks (e.g., cleaning up).

Moderate

– The child can do some self-care activities with training and help. Basic home tasks can be done, but will likely be delayed and need continued help into adulthood. The child can learn and join in recreational activities.

Severe

– The child’s development of all daily living skills is very delayed, but they can still do basic self-care or home chores with help. The child can learn and join in basic recreational activities with support. Self-injury or other concerning behaviors may be present.

Profound

– The child will remain dependent on caregivers for all daily living tasks, although some may join in basic self-care or home chores with help. Recreational activities are limited, but may include listening to music, watching movies, or going for supervised walks, as well as water activities with help. Comorbid motor or sensory impairments may stop participation in activities. Self-injury or other concerning behaviors may be present.

Intellectual Development Disorder facts

Worldwide prevalence:

The condition affects about 1% of the world’s population.

Impact of the condition in Brazil:

Despite limited data, the estimated prevalence of intellectual development disorder is about 0.5% in children (5-9 years).

Gender ratio:

Boys are more frequently diagnosed with DID than girls, although this may vary with severity and associated comorbidities.

What are the associated factors for Intellectual Developmental Disorder?

IDD is often linked with things that happen early in a child’s life, like head injuries or being near harmful substances (e.g., lead). Some factors linked to IDD include:

– Genetic and familial factors: Some genetic syndromes and chromosomal disorders can lead to intellectual problems, like Down syndrome, 22q11.2 deletion syndrome, fragile X syndrome, Williams syndrome, and Prader-Willi syndrome.

– Prenatal development factors: Being born too early, before 25 weeks.

– Complications during pregnancy: Some infections during pregnancy, a mother using illegal drugs or alcohol, or being exposed to toxins (e.g., lead, mercury, certain medicines), or not getting enough nutrients.

– Complications during childbirth: Serious issues like lack of oxygen for the baby, heavy bleeding for the mother, or accidents during delivery.

– Complications after birth and early childhood: Serious brain infections (e.g., meningitis or encephalitis), bad accidents affecting the brain, repeated seizures, or severe abuse.

What other disorders co-occur with Intellectual Developmental Disorder?

Children with IDD often have other neurodevelopmental and medical conditions three to four times more than other kids. Common disorders that occur with IDD include Autism Spectrum Disorder (ASD), Attention Deficit/Hyperactivity Disorder (ADHD), depression, anxiety, bipolar disorder, and conduct disorder. Common physical issues include thyroid problems, seizures, heart issues, obesity, and constipation. It is important to work with a pediatrician to prevent, find, and manage these conditions. This includes regular check-ups, early hormone checks, routine lab work, and clinical assessments.

How is Intellectual Developmental Disorder treated?

IDD is a lifelong condition, but there are ways to lessen its effects and improve life quality. Special education and rehab programs can help children learn important social and practical skills needed for school and, sometimes, living independently as adults. The sooner the problems are found and diagnosed, the better the outcome. Different interventions can help families in various ways:

– Preventing or minimizing the worsening of symptoms: Following medical advice on regular checks and managing other medical issues can help reduce mental health problems. Early intervention, which includes diagnostic and therapeutic services for children under 3, can greatly improve learning, behavior, and function.

– Limiting daily life impairment: Services like occupational therapy, physical therapy, speech-language therapy, and family counseling can improve daily life, cognitive, and social skills. Psychiatric medications may help with behavior and emotional issues.

– Supporting better functioning and quality of life: These interventions help children and teens with IDD in their education, socializing, and job training, preparing them for community integration as adults. Adults with mild and some with moderate IDD may live independently.

References

Clinical description, symptoms, and diagnostic information

– American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders: Fifth edition text revision DSM-5-TR. American Psychiatric Association Publishing.

– Child Mind Institute. (2021). Quick guide to intellectual development disorder. Child Mind Institute. Retrieved 11/17/22, from https://childmind.org/guide/quick-guide-to-intellectual-development-disorder/

– World Health Organization. (2022). 6A00 Disorders of intellectual development. In International statistical classification of diseases and related health problems (11th ed.). https://icd.who.int/browse11/l-m/en#/http%3a%2f%2fid.who.int%2ficd%2fentity%2f605267007

Facts

– American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders: Fifth edition text revision DSM-5-TR. American Psychiatric Association Publishing.

– Institute for Health Metrics and Evaluation (IHME). (2019). GBD compare data visualization. Seattle, WA: IHME, University of Washington. Available from http://vizhub.healthdata.org/gbd-compare. (Accessed 11/15/2022)

– Kendler, K. S. (2013). What psychiatric genetics has taught us about the nature of psychiatric illness and what is left to learn. Molecular Psychiatry, 18(10), 1058–1066. https://doi.org/10.1038/mp.2013.50

– Maulik, P. K., Mascarenhas, M. N., Mathers, C. D., Dua, T., & Saxena, S. (2011). Prevalence of intellectual disability: A meta-analysis of population-based studies. Research in Developmental Disabilities, 32(2), 419–436. https://doi.org/10.1016/j.ridd.2010.12.018

– Polyak, A., Rosenfeld, J. A., & Girirajan, S. (2015). An assessment of sex bias in neurodevelopmental disorders. Genome Medicine, 7(1), 94. https://doi.org/10.1186/s13073-015-0216-5

– Solmi, M., Radua, J., Olivola, M., Croce, E., Soardo, L., Salazar de Pablo, G., Il Shin, J., Kirkbride, J. B., Jones, P., Kim, J. H., Kim, J. Y., Carvalho, A. F., Seeman, M. V., Correll, C. U., & Fusar-Poli, P. (2022). Age at onset of mental disorders worldwide: Large-scale meta-analysis of 192 epidemiological studies. Molecular Psychiatry, 27(1), 281–295. https://doi.org/10.1038/s41380-021-01161-7

Associated factors

– American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders: Fifth edition text revision DSM-5-TR. American Psychiatric Association Publishing.

– Glasson, E. J., Buckley, N., Chen, W., Leonard, H., Epstein, A., Skoss, R., Jacoby, P., Blackmore, A. M., Bourke, J., & Downs, J. (2020). Systematic review and meta-analysis: Mental health in children with neurogenetic disorders associated with intellectual disability. Journal of the American Academy of Child & Adolescent Psychiatry, 59(9), 1036–1048. https://doi.org/10.1016/j.jaac.2020.01.006

– Lichtenstein, P., Tideman, M., Sullivan, P. F., Serlachius, E., Larsson, H., Kuja‐Halkola, R., & Butwicka, A. (2022). Familial risk and heritability of intellectual disability: A population‐based cohort study in Sweden. Journal of Child Psychology and Psychiatry, 63(9), 1092–1102. https://doi.org/10.1111/jcpp.13560

– Kendler, K. S. (2013). What psychiatric genetics has taught us about the nature of psychiatric illness and what is left to learn. Molecular Psychiatry, 18(10), 1058–1066. https://doi.org/10.1038/mp.2013.50

Co-occurring disorders

– American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders: Fifth edition text revision DSM-5-TR. American Psychiatric Association Publishing.

– Buckley, N., Glasson, E. J., Chen, W., Epstein, A., Leonard, H., Skoss, R., Jacoby, P., Blackmore, A. M., Srinivasjois, R., Bourke, J., Sanders, R. J., & Downs, J. (2020). Prevalence estimates of mental health problems in children and adolescents with intellectual disability: A systematic review and meta-analysis. Australian & New Zealand Journal of Psychiatry, 54(10), 970–984. https://doi.org/10.1177/0004867420924101

Interventions

– Ke, X., & Liu, J. (2020). Intellectual disability. In J. M. Rey & A. Martin (Eds.), JM Rey’s IACAPAP textbook of child and adolescent mental health (p. 25). International Association for Child and Adolescent Psychiatry and Allied Professions.

– Sheerin, F., Eustace-Cook, J., Wuytack, F., & Doyle, C. (2021). Medication management in intellectual disability settings: A systematic review. Journal of Intellectual Disabilities, 25(2), 242–276. https://doi.org/10.1177/1744629519886184