A condition of arrested or incomplete development of the mind, which is especially characterised by impairment of skills, manifested during the developmental period, which contribute to the overall level of intelligence, i.e. cognitive, language, motor, and social abilities
Aetiology
Co-morbidities
People with ID are 3 x more likely to experience another psychiatric disorder than the general population
Clinical presentation
Severity of ID
Borderline ID - IQ 70-84
Mental age 12 to under 15 years
Mild ID - IQ 50-69
Mental age 9 to under 12 years
Most common
Delayed speech - able to use everyday speech
Full independence - self care, practical and domestic skills
Difficulties in reading and writing
Capable of unskilled or semi-skilled work
Problems if social or emotional immaturity
Rarely organic aetiology
Moderate ID - IQ 35-49
Mental age 6 to under 9 years
Slow with comprehension and language
Limited achievements
Delayed self care and motor skills
Simple practical tasks - often with supervision
Usually fully mobile - physically active
Discrepant profiles
Majority organic aetiology
Epilepsy and physical disability common
Severe ID - IQ 20-34
Mental age 3 to under 6 years
Generally more marked impairment than in moderate ID and achievements more restricted
Epilepsy
Profound ID - IQ < 20
Mental age less than 3 years
Severe limitation in ability to understand or comply with requests or instructions
Little or no self care
Often severe mobility restriction
Basic or simple tasks may be acquired
Investigations
Psychometric assessment - most commonly used Wechsler Adult Intelligence Scale (WAIS)
Diagnosis based on clinical findings
Management
Psychological treatment
Behavioural e.g. teach/improve basic skills, relaxation techniques
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