The World Health Organization (WHO) has defined learning disabilities as a state of arrested or incomplete development of mind. Somebody with a general learning disability is said to have a significant impairment of intellectual, adaptive and social functioning. A learning disability is not acquired in adulthood and is evident from childhood.

Classification

• Mild learning disability - IQ 50-70, approximately 85% of cases: most can lead normal lives except that they may need assistance in handling difficult situations.
• Moderate - IQ 35-49, approximately 10% of cases: they use simple language when talking but understand speech better. After training, the patient can generally attend to the basic tasks of life but more complex activities, such as using money, usually require support within a special residential environment.
• Severe - IQ 20-34, approximately 3-4% of cases: many are able to look after themselves with careful supervision.
• Profound - IQ less than 20, approximately 1-2% of cases: the development level of a one year-old baby across a range of parameters and so requiring intensive help and supervision in all activities.

Epidemiology

• Epidemiological research shows a prevalence of intellectual disability of about 0.7%.¹
• The number of people with intellectual disabilities increased by 53% over the 35-year period from 1960 to 1995 (as a result of improved socio-economic conditions, intensive neonatal care and increasing survival).²

Causes

• Genetic: chromosome disorders - trisomy (e.g. Down's syndrome), deletion (e.g. cri du chat syndrome), sex chromosome anomaly (e.g. Fragile X syndrome, Klinefelter's syndrome, Turner's syndrome).
• Metabolic: amino acid (e.g. phenylketonuria), carbohydrate (e.g. galactosaemia), lipid (e.g. Tay-Sachs disease, Gaucher's disease, Niemann-Pick disease), mucopolysaccharidoses (e.g. Hurler's syndrome).
• Cerebral degeneration: e.g. gangliosidoses, leukodystrophies.
• Structural disorders: e.g. tuberous sclerosis, familial hydrocephalus, neurofibromatosis.
• Intrauterine:
  • Nutritional deficiency: e.g. iodine deficiency.
  • Congenital infection: e.g. cytomegalovirus, rubella, toxoplasmosis.
• Drugs: e.g. phenytoin, alcohol.
• Cerebral malformations: e.g. holoprosencephaly, lissencephaly.
• Perinatal:
  • Antenatal: e.g. pre-eclampsia, antepartum haemorrhage, premature labour.
  • Intrapartum: e.g. prolonged labour, trauma, asphyxia.
• Neonatal: e.g. intraventricular haemorrhage, hypoglycaemia, meningitis, severe neonatal jaundice.
• Postnatal:
  • Accidental or nonaccidental injury.
  • Infection: e.g. encephalitis, meningitis.
  • Anoxia: asphyxia, status epilepticus, near drowning.
  • Metabolic, endocrine: hypoglycaemia, hypernatraemia, hypothyroidism.
  • Poisoning: lead, carbon monoxide.
  • Malnutrition.

Presentation

• The presentation will depend on the cause.
• Generally poor performance on tasks such as learning, short-term memory and problem solving.
• Frequently associated with specific congenital syndromes, e.g. Down's syndrome, fragile X syndrome.
• Assessment needs to consider the possible cause, e.g. family history, birth history, functional disability and associated medical, psychological and social difficulties.

Associated problems

• Physical:
  • Motor and mobility problems.
  • Abnormalities of movement.
  • Speech, hearing and visual impairment.
  • Epilepsy.
  • Urinary and faecal incontinence.
  • There is evidence of increased risk of obesity, fractures, poor oral health (including dental caries and loss of teeth), constipation and gastro-oesophageal reflux disease.¹
• Psychological (the following are more common in patients with learning disabilities):
  • Schizophrenia.
  • Anxiety and depressive disorders.
  • Personality disorder.
  • Early onset dementia.
  • Autism.
  • Hyperactivity and attention-deficit hyperactivity disorder.
  • Eating disorders, including rumination, food faddiness, anorexia nervosa and bulimia nervosa are common.
• Behaviour:
  • Threatening the safety of themselves or others.
  • Seemingly violent but harmless behaviour (often interpreted as aggression).³
  • Temper tantrums.
  • Criminal activity.
• Sleep disorders.

Communication¹

• Focus on abilities and not disabilities. Talk respectfully, take time and explain what is happening.
• Always greet the person first, before addressing the accompanying person.
• Check if your patient has verbal capacities. There may be an imbalance between receptive and expressive language skills.
• Obtain the medical history as far as possible from the patient; otherwise an accompanying person should complete it.
• Make it clear that, if the patient wants the accompanying person to leave at any moment during the consultation, he or she can indicate that.
• For people who are nonverbal, there is a large variety of communication aids, including body language (e.g. gestures or facial expressions), sign language, pictures and electronic devices. Ask the accompanying person how they know what the patient wants.

Management

• Management includes multidisciplinary support for both the child and the rest of their family. The person with mental handicap and their carer(s) and family need a great deal of physical and emotional support.
• Psychological, psychosocial, and educational interventions for deprived children with low IQ have been shown to have positive effects on behaviour, overall adjustment and possibly also on IQ.³
• Behavioural treatment methods for self-injury in learning disability are probably effective if used systematically by people who are well trained in such methods.³
• Psychotropic drugs are often used but rarely produce significant benefits.
• Direct support and coaching of young people with learning disability are efficient ways to improve their integration into employment.³
• If a person presents with challenging behaviour, assess for physical (for example, pain such as toothache, earache) and other sources of discomfort before treating the behaviour as psychiatric and prescribing psychotropic drugs.¹

Annual health screening

NHS Employers and the British Medical Association (BMA) have published guidance on a number of new 'Directed Enhanced Services' for GP practices, which include annual health checks for adults with learning disabilities.⁴

• A recent randomised controlled trial on annual health screening in people with intellectual disabilities found an improvement in health in the intervention group.¹
• Health management plans should be evaluated annually and should include case finding, appropriate monitoring of existing health needs, promotional activities and disease prevention.¹
• As a minimum, the health check should include:⁵
  • A review of physical and mental health with referral through the usual practice routes if health problems are identified:
    • Health promotion.
    • Chronic illness and systems enquiry.
    • Physical examination.
    • Epilepsy.
    • Behaviour and mental health specific syndrome check.
  • A check on the accuracy of prescribed medications.
  • A review of co-ordination arrangements with secondary care.
  • A review of transition arrangements where appropriate.
• One example of a form that can be used is the Cardiff Health Check for People with a Learning Disability.⁶

Informed consent¹

See also separate articles Consent to Treatment and Mental Capacity Act.

• There may be an incongruence between receptive and expressive verbal skills. It may take time to realise that, although a person is giving clear answers, he or she does not understand the question.
• Assessment of mental capacity is specific for each individual decision at any particular time. People are considered to lack capacity if they have an impairment that causes them to be unable to make a specific decision. The person should be able to understand, retain and weigh the information provided and communicate their decision.

Complications

• Behavioural problems: these include distractible, overactive, impulsive, repeated self-injury, stereotyped repetitive and purposeless activities.
• Sexual problems: curiosity about other people's bodies may be misunderstood as sexual; inappropriate behaviour, e.g. masturbation in public.
• Physical disorders are more frequent. The most common physical health problems are epilepsy, mobility problems, and sensory problems.¹
• Disorders of vision and hearing are also more frequent.
• Effects on the family: parental rejection, physical and emotional stress in caring for a child with learning disability, difficulty with family dynamics with other siblings, and increasing difficulty, as the child gets older, with isolation, contraception, etc.

Prognosis

• Most adults with learning disability have very limited economic resources.
• People with severe learning disability have a particularly poor outlook. Those with mild learning disability and borderline intelligence also do poorly in terms of adaptive functioning.³
• Life expectancy is reduced in those with learning disability. Non-mobile children and those incapable of feeding themselves may be at particular risk of a short life expectancy.
• Both the scope and pattern of disease mortality and cause-specific mortality tend to become increasingly similar to those of the general population after the age of 40 years.³

Prevention

• Early and effective management of problems during the antenatal period and during intrapartum care.
• Early and effective management of problems in the neonatal period and early childhood.

Document references

1. van Schrojenstein Lantman-de Valk HM, Walsh PN; Managing health problems in people with intellectual disabilities. BMJ. 2008 Dec 8;337:a2507. doi: 10.1136/bmj.a2507.
2. Cooper SA, Melville C, Morrison J; People with intellectual disabilities. BMJ. 2004 Aug 21;329(7463):414-5.
3. Gillberg C, Soderstrom H; Learning disability. Lancet. 2003 Sep 6;362(9386):811-21. [abstract]
4. Health Checks for People with Learning Disabilities, Dept of Health, February 2009
5. Clinical directed enhanced services (DESs) for GMS contract 2008/09; Learning disabilities; March 2009
6. Cardiff Health Check for People with a Learning Disability

Acknowledgements