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Psychiatric Causes of Intellectual Disabilities

Tammy Reynolds, B.A., C.E. Zupanick, Psy.D. & Mark Dombeck, Ph.D.

Autism Spectrum Disorder (ASD)

A leading cause of intellectual disabilities (ID, formerly mental retardation) is autism spectrum disorder (ASD). A person may be diagnosed with both ASD and an ID. ASD has two primary symptoms. First, people with ASD have trouble with communication and social interaction. Second, they demonstrate repetitive patterns of behaviors, interests, or activities. Some examples are repetitive speech, ritualized patterns of behavior, or fixation upon certain objects. Approximately 40% of people with ID will also have ASD. However, nearly 70% of people with ASD also have ID (reported in La Malfa, G., Lassi, S., Bertelli, M., & Placidi, G.F., (2004). See also http://www.cdc.gov). Thus, while ASD and ID share some similarities, they are not the same.

Although similar, the two disorders are often difficult to tease apart. People with ASD might appear to meet the criteria for ID because their IQ scores are low. However, these low test scores may not reflect intelligence per se. Instead, the low scores might result from problems with test taking itself. These test-taking problems result from communication and social limitations. Since IQ testing relies on both of these abilities to some extent, IQ scores may be artificially low. Some children with ASD may have an average IQ. However, they cannot demonstrate their abilities because they cannot communicate their understanding of the testing protocols. In contrast, children with intellectual disabilities lack this intellectual capacity or understanding. Although the two conditions are distinct, they can and do frequently co-occur. More information about co-occurring disorders is found in the Diagnostic Section.


Genetic Causes of Intellectual Disabilities: Prader-Willi Syndrome (PWS)

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Resources

  • Articles

    • Introduction to Intellectual Disabilities
    • Causes of Intellectual Disabilities
    • Diagnosis of Intellectual Disabilities
      • The Diagnosis of Intellectual Disabilities
      • Psychological Tests and Intellectual Disabilities
      • Psychological Tests and Intellectual Disabilities Continued
      • Tests of Adaptive Functioning
      • Diagnostic Criteria for Intellectual Disabilities: DSM-5 Criteria
      • The American Association on Intellectual and Developmental Disabilities (AAIDD) Diagnostic Criteria for Intellectual Disability
      • Comparing the APA and the AAIDD Diagnostic Criteria for Intellectual Disability
      • Intellectual Disability and Severity Codes
      • Intellectual Disability and Other Psychiatric Disorders
    • Historical & Contemporary Perspectives of Intellectual Disabilities
      • Historical And Contemporary Perspectives on Intellectual Disabilities
      • Early Medical Explanations of Intellectual Disability
      • History of Stigmatizing Names for Intellectual Disabilities
      • History of Stigmatizing Names for Intellectual Disabilities Continued
      • Reducing the Stigma of Intellectual Disabilities: The Evolution of Modern Medical Explanations
      • Paving the Way to a Modern Conception of Intellectual Disability: Advancements in Intelligence Testing
      • Advancements in Genetic Research
      • Social and Political Controversies Associated with Intellectual Disabilities
      • Reproductive Rights for People with Intellectual Disabilities
    • Intellectual Disabilities & Supportive Rehabilitation
      • Intellectual Disabilities and Supportive Rehabilitation: Developing an Individualized Support Plan (ISP)
      • Educational Supports and Individual Educational Plans (IEPs)
      • The Choice of Educational Settings: The Pros and Cons of Mainstreaming Children With Intellectual Disabilities
      • Effective Teaching Methods for People With Intellectual Disabilities
      • Applied Behavioral Analysis (ABA) and Intellectual Disabilities
      • Physical Therapy and Sensory Skills Training
      • Individualized Support Plans: Adaptive Functioning & Life Skills
      • Social Skills Training
      • Supported Employment and Integrated Work Sites
      • Supported Housing and Community Integration
      • Therapies for Intellectual Disabilities and Outdated/Unproven Treatments
    • Support for Families of People with Intellectual Disabilities
      • Additional Support Services for People with Intellectual Disabilities and Their Families: Community Supports
      • Additional Support Services: Financial Supports
      • Additional Support Services: Family Supports
      • Additional Support Services: Advocacy and Legal Supports
    • Intellectual Disabilities Summary & Conclusion
      • Intellectual Disabilities Summary and Conclusion
    • Intellectual Disabilities Resources & References
      • Intellectual Disabilities Resources and References
      • Intellectual Disabilities Document Revision History
  • Book & Media Reviews

    • A Special Education
    • Living with Mild Cognitive Impairment
  • Videos

    • What is Intellectual Disability?
    • Let's Talk About Intellectual Disabilities: Loretta Claiborne
    • What Causes an Intellectual Disability?
    • What Is An Intellectual Disability?
    • What's disability to me? Mia's story.
    • Primary Care of Children and Young Adults with Down Syndrome
    • Dr. Tim Shriver: Intellectually Different ... Not Disabled
    • Living with Down Syndrome: Parents, Health Professionals and Personal Perspectives