Intellectual Disability: What is it? and what can I do about it?

Intellectual Developmental Disorder (IDD), formerly known as intellectual disability, is a neurodevelopmental condition characterised by significant limitations in both intellectual and adaptive functioning. It is diagnosed based on the criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR). People with IDD are eligible for NDIS funding for practical and therapeutic support. Formal assessment and diagnosis is required to apply for this funding.

Levels of Intellectual Disability

IDD is characterised into three levels largely based on level of adaptive functioning. Adaptive functioning refers to a person's ability to effectively navigate daily life tasks (e.g. cooking, self-care, transport) and challenges, such as communication, self-care, and social interactions:

• Mild: Individuals with mild IDD typically demonstrate adaptive functioning at a level corresponding to a developmental age of 9-12 years. They can often acquire basic academic skills, live independently with minimal support, and hold jobs.

• Moderate: Individuals with moderate IDD exhibit adaptive functioning equivalent to a developmental age of 6-9 years. They may require assistance with daily living activities and often benefit from vocational training and supported living arrangements.

• Severe: Individuals with severe IDD demonstrate adaptive functioning comparable to a developmental age of 2-6 years. They require significant support in all aspects of life, including communication, mobility, and self-care.

Diagnosis of Intellectual Disability

The diagnosis of IDD involves a comprehensive assessment that evaluates both cognitive and adaptive functioning. Cognitive assessment typically includes standardized intelligence tests, such as the Wechsler Intelligence Scale for Children (WISC-V). Adaptive functioning assessment typically includes the person being assessment and/or those who know them well completing online questionnaires (e.g. ABAS; Vineland). If someone is assessed and diagnosed for ASD, they will be eligible for NDIS funding.

Recommendations and Treatment Options

Recommendations for individuals with IDD often include:

• Educational modifications: Tailored instruction to address individual learning needs and strengths.

• Behavioral strategies: Techniques to promote adaptive behaviors and reduce challenging behaviors.

• Therapies: Speech-language therapy, occupational therapy, and physical therapy to support communication, daily living skills, and motor development.

• NDIS recommendations: Funding and support through the National Disability Insurance Scheme (NDIS) to access essential services and supports.

Treatment options

• NDIS: The NDIS generally funds individuals with IDD to gain access to supports such as community access, behaviour support, travel, occupational therapy, speech therapy, and psychology.

• Medication: To manage co-occurring mental health conditions such as anxiety or depression.

• Early intervention: Providing support and services from a young age to optimize development and outcomes.

• Family support: Counseling and resources for families to cope with the challenges and demands of raising a child with IDD.

It is important to note that IDD is a lifelong condition that requires ongoing support and individualised interventions. With appropriate support, individuals with IDD can lead fulfilling and meaningful lives.

Referral for assessment

If you suspect one of your clients or someone you know may experience intelletual functioning difficulties and may meet criteria for an IDD diagnosis, please contact us to book an appointment. You can also find other resources and articles on our website which may help. 

Jordi Tome - BA(Psych), MClinPsych

Clinical Psychologist 

Director, Jigsaw Psychology and Assessments www.jigsawpsych.com.au