Description of intellectual disability

People with intellectual disability have a wide range of skills, capabilities, interests, strengths and needs. It is important not to make assumptions about these. Each person with intellectual disability is unique and will require an individualised approach to rneeting their personal healthcare needs.

Intellectual disability (also known as intellectual developmental disorder) is a conditon involving impairment of general intellectual abilities which begins during the developmental period and impacts significantly on a person's adaptive functioning.¹ Impairments in adaptive functioning can occur in three areas, including:

• conceptual, e.g. language, reading, writing
• social, e.g. empathy, interpersonal communication skills, social judgement
• practical, e.g. personal care, self-management, lifestyle.

Developmental disability is a broad term used to describe several physical and cognitive conditions arising in the developmental period.

Assessment

Assessment is usually based on the severity of deficits in adaptive functioning. This can be determined by clinical and standardised cognitive tools. Formal testing of intellectual abilities will enhance the person’s assessment. The severity of intellectual disability can be described clinically as mild, moderate, severe or profound.

Functional capacity

A person's functional capacity may be affected by their health and other factors, including:

• the specific characteristics and aetiology of their diagnosis
• related co-morbidities (physical, mental or behavioural)
• family and community supports available
• access to health services (including specialised health services)
• understanding of, and ability to act on, preventative health advice
• housing
• financial situation
• educational and work opportunities
• challenging behaviour
• other health conditions (diagnosed or undiagnosed).

Health conditions common to the general population, but also experienced by people with intellectual disability (such as gastro-oesophageal reflux, heart conditions, mental ill-health, presence of autism, sight and hearing difficulties), all compound the impact of a person’s intellectual disability on their functional capacity.

Related health conditions

Intellectual disability can be confused with other conditions that have subsequent loss of cognitive and adaptive functions. For example, acquired brain injury can affect a person’s functional capacity and may be caused by accident, abuse, stroke or drugs and alcohol. If this injury happens during the developmental period and persists, the person is considered to have an intellectual disability.

Dementia is different from intellectual disability in that it is usually not a developmental disorder, however a small number of children do develop dementia as part of their life-limiting condition. It is usually characterised by progressive deterioration in cognitive function which impact the person’s ability to carry out their daily function. Sometimes dementia may also affect people with intellectual disability.

There is a link between early onset Alzheimer’s disease and Down syndrome.²

The right to self-determination

People with intellectual disability have the right to make choices about their lives.

In order to understand and communicate their choices and preferences, people with intellectual disability may require support.³

Health professionals may also require expert and individualised support to understand the person's needs and choices and their role in the process.

Complex needs

In all age groups, people with intellectual disability experience a higher prevalence of health conditions. These can either be associated with their disability (as part of a syndrome) or be direct or indirect consequences of the intellectual disability. Such health conditions are often multiple and complex. They may include sensory impairment and epilepsy, physical illness or disability as well as mental health and behavioural challenges. Health conditions may also exacerbate functioning deficits in people with intellectual disability. For example, a person with intellectual disability might have difficulty with muscle coordination for chewing and swallowing. Positioning difficulties from scoliosis may further limit their ability to chew and swallow food, which may increase their risk of aspiration pneumonia.

Chronic, complex health conditions are increasing across the age spectrum. One cohort are those with conditions of childhood which may have been life limiting in the past. Now these people are surviving well into adulthood with a spectrum of needs and disabilities. For example, people with Down syndrome are now living into older age.

Factors that contribute to the complexity of health needs

• Multiple disabilities
• Severity of intellectual disability
• Dual diagnosis (e.g. intellectual disability and mental illness)
• Severe, multiple or deteriorating health conditions
• Behaviours involving harm to self or others
• Alcohol and/or drug issues
• Issues relating to past experience of trauma or neglect.

Situational factors can include:

• socio-economic disadvantage
• lack of natural support (Natural supports are the help and care that someone receives from relationships that occur in everyday life, from friends, family or the community.)
• family or carer stress
• breakdown in care arrangements
• young people leaving care
• involvement in the criminal justice system
• multiagency involvement in the provision of support.

Cognitive and communication impairments mean people with intellectual disability often rely on carers or proxies to access healthcare. People with complex support needs may find additional challenges to accessing timely and high quality healthcare. This happens when health services are not accessible and/or staff are not trained in working with people with intellectual disability.

Providing healthcare

A particular challenge for health services is ensuring that all people with intellectual disability, are catered for by the mainstream health system, even when their health needs are complex.

This has implications for how health services coordinate healthcare, develop partnerships with the disability sector and recognise the individual’s need to navigate a range of healthcare specialties, along with disability, educational and social services. Integrated care is the engagement of primary care providers, networks and partnerships between providers and with people with intellectual disability and their families. Integrated care is important to support the healthcare needs of people with intellectual disability.

1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders: DSM-5. 5th ed. Washington, DC, USA: American Psychiatric Association: 2013. DOI: db29.linccweb.org/10.1176/ appi. books
2. Torr J, Alzheimer's Australia, Down Syndrome Association of Victoria, et al. Down syndrome and Alzheimer's disease. Victoria: Centre for Developmental Disability Health; 2009.
3. Capacity Australia. About Decision Making Capacity. Sydney: Capacity Australia; 2017.