Table AIII.

Main characteristics of severe IDD

As children individuals with severe IDD show gross impairments in attainment of all developmental milestones

They cannot speak beyond phrases or simple sentences. They often use signs or gestures to communicate

They may learn to read and write very simple words with intensive training

The person needs assistance with basic self-care activities such as toileting functions; however, by adulthood, they are likely to have mastered some of these with intensive training

Usually, people with severe IDD are mobile, but may be uncoordinated and lack adequate visuo-motor skills. The majority shows some evidence of social development and enjoy interaction

As an adult, most are able to perform very simple repetitive tasks household chores such as fetching, carrying and cleaning in closely supervised settings. They typically require considerable and regular support from others throughout the entire day

In general the behavioural, emotional, and social difficulties of persons with severe IDD differ largely from the general population

Persons with severe IDD may often have a psychiatric illness that goes undiagnosed due to limitations in verbal expression, and differences in presentation

Co-occurring psychiatric disorders must be assessed using complementary diagnostic guidelines adapted for IDD

These persons show more associated medical problems such as epilepsy, sensory impairment, gastro-intestinal disorders, and cerebral palsy than persons with mild or moderate IDD

The IQ is usually in the range 20–34. It should be taken into account that the accuracy of IQ measurements is decreased in this group

Profound IDD

In childhood, they show profound impairments in attainment of milestones in all areas of development; for instance, a two year-old-child with profound IDD is not able to sit without support, reach for objects, recognize close family members, or localize sounds

Persons with Profound IDD are unable to understand or comply with most except the simplest of verbal requests or instructions. They are capable of rudimentary forms of non-verbal communication and may develop vocabulary of a few words or phrases understood by caregivers

Persons with profound IDD are more likely to be immobile or severely restricted in mobility than persons at other ability levels

They are often incontinent, possess little or no ability to care for themselves, and so require intense assistance, for nearly all self-care activities, including attention during the night

In general the behavioural, emotional, and social difficulties of persons with profound IDD differ largely from other clinical severity levels of IDD. Psychiatric illness may go undiagnosed due to severe limitations in verbal expression and differences in presentation. Co-occurring psychiatric disorders must be assessed using complementary diagnostic guidelines adapted for IDD

They have more associated medical problems than persons with less severe IDD. Severe neurological or other locomotor disabilities affecting mobility are very common, as are epilepsy and visual/hearing impairments, and gastro-intestinal problems such as gastro-oesophageal reflux disorder and constipation

The IQ is usually under 20, but this measure is of limited value in this group