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Signs, symptoms and testing of intellectual disability

Intellectual disability (ID) is identified as mild (most people with ID are in this category), moderate or severe
Child playing with educational toy
© University of Bath

Intellectual disability (ID) is identified as mild (most people with ID are in this category), moderate or severe. The symptoms of ID begin during childhood or adolescence. Delays in language or motor skills may be seen by age two. However, mild levels of ID may not be identified until school age when a child may have difficulty with academics.

There are many signs of ID. For example, children with ID may:

  • Sit up, crawl, or walk later than other children
  • Learn to talk later, or have trouble speaking
  • Find it hard to remember things
  • Have trouble understanding social rules
  • Have trouble seeing the results of their actions
  • Have trouble solving problems

There may be deficits in intellectual functions which could affect:

  • Language development
  • Reasoning
  • Problem solving
  • Planning
  • Abstract thinking
  • Judgement
  • Academic learning
  • Learning from experience

The level of support needed for adaptive functioning (i.e. performance of basic life skills) determines the severity level for ID. The DSM-5 breaks down the signs and symptoms of adaptive functioning deficits across three domains: conceptual, social and practical:

Conceptual Domain

  • Slow language development (children learn to talk later, if at all)
  • Slow development of pre-academic skills
  • Difficulties in academic learning (reading, writing, mathematics)
  • Difficulty understanding concepts of time and money
  • Problems with abstract thinking (concrete approach to solving problems)
  • Difficulties in executive function (ie planning, strategising, priority setting, cognitive flexibility)
  • Problems with short-term memory
  • Difficulties with functional use of academic skills such as money management and time management

Social Domain

  • Limitations in language and communication skills
  • More concrete and less complex spoken language (if used), compared with peers
  • Limited vocabulary and grammatical skills
  • Receptive language that may be limited to comprehension of simple speech and gestures
  • Communication that may occur through nonspoken means only – such as gestures, signs, facial expressions, and other forms of augmentative and alternative communication (AAC)
  • Social Skills
  • Immature social judgement and decision-making
  • Difficulty understanding peer social cues and social rules
  • Emotional and behavioural regulation difficulties that may adversely affect social interactions

Practical Domain

Requiring different levels of support for daily life activities such as:

  • Personal care
  • Complex tasks (eg shopping, transportation, care organisation, meals, money management)
  • Employment
  • Health care and legal decisions
  • Household tasks
  • Recreational skills

More information is available in this article on intellectual disability.

Testing (Screening)

In their article Screening for Intellectual Disability in Children: A Review of the Literature, McKenzie and Megson looked at everything available in the area in 2012. They concluded:

there is not, as yet, a screening tool which can reliably identify children with a probable intellectual disability. Further research in this area is needed.
© University of Bath
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