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What is Intellectual Disability? Causes and Presentations

What is Intellectual Disability? Causes and Presentations. Dr Simon Bonell Consultant Psychiatrist in Intellectual Disabilities Plymouth Community Healthcare (CIC). MRCPsych Course. Overview. Definition of ID Epidemiology of ID Causes of ID

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What is Intellectual Disability? Causes and Presentations

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  1. What is Intellectual Disability?Causes and Presentations Dr Simon Bonell Consultant Psychiatrist in Intellectual Disabilities Plymouth Community Healthcare (CIC) MRCPsych Course

  2. Overview • Definition of ID • Epidemiology of ID • Causes of ID • Cause of ID and relevance to psychiatric disorders • Pathoplastic effect of ID on psychopathology • Assessment and diagnostic challenges • DC-LD approach to diagnosis

  3. First a note on terminology Learning Difficulties Learning Disabilities Intellectual Disability

  4. First a note on terminology Subnormal Mental retardation Imbecile

  5. What is the definition of ID?

  6. What is the definition of ID? • Reduced level of intellectual functioning • Reduced ability to adapt to the daily demands of a normal social environment • Manifested during the developmental period

  7. How do you diagnose ID?

  8. How do you diagnose ID? • Clinical assessment • Adaptive behaviour • Psychometric test performance

  9. Clinical assessment • Developmental history • Family history • Childhood / educational history • Occupational history • Social history • Level of functioning • Past medical and psychiatric history • Forensic history • Pre-morbid personality

  10. Clinical assessment • Appearance and Behaviour • Speech • Mood • Thoughts • Perceptions • Cognition • Insight

  11. The role of IQ • Intelligence Quotient (IQ) measures a range of different intellectual abilities • In most people skills develop to a similar level • Large discrepancies can occur esp. in ID • IQ scores summated to give verbal and performance score and a full scale IQ • Normal distribution

  12. The role of IQ • Mean IQ of population is 100 • IQ of 70 represents 2 standard deviations from the mean • Mild ID: 50 – 69 • Moderate ID: 35 – 49 • Severe ID: 20 – 34 • Profound ID: <20

  13. Epidemiology • 2.27% of the population have IQ<70 • Add those with specific causes • Overall prevalence rate between 2 – 3% • 75 – 90% have mild ID

  14. A note on “mental age” • Adult with profound ID has an equivalent mental age of 0 – 3 years • Unable to understand abstract concepts • However, has lifelong experiences, skills development and adult biological urges and drives • “Mental age” should not be used for adults

  15. Clinical descriptors of ID • Mild ID • The majority of people with ID • Verbal communication usually reasonable but note receptive / expressive mismatch and overestimation of understanding and abilities • Usually only minimal support with basic self care but some deficits in more complex aspects of social functioning (finance / employment) • Support level ranges from none to very high levels (if significant risks are present)

  16. Clinical descriptors of ID • Moderate ID • Verbal communication more reduced. Can generally understand short simple sentences • Higher levels of support with self care usually required. Difficulties in adapting to new situations (e.g. may learn to use a bus independently but not able to work out a new route) • Moderate to high levels of support required

  17. Clinical descriptors of ID • Severe / profound ID • Little expressive verbal ability but note understanding may be better • Needs high levels of support with basic self care • Increasing rates of sensory deficits and physical disabilities

  18. Why do we label a group of people as having “ID”

  19. Vulnerability • To mental illness • 40% of people with ID have “mental disorder” • To physical illness • To poor treatment by society

  20. Causes of ID • “Idiopathic” ID accounts for 30 – 50% of cases • Most common inherited cause of ID: Fragile X • Most common chromosomal defect: Down Syndrome • Why is the cause of ID relevant to the psychiatrist?

  21. Behavioural phenotypes • Prader-Willi: Hyperphagia, food ideation • Lesch-Nyhan: Extreme self mutilation • Smith-Magenis: Objects in orifices, self hugging • 22q11.2 deletion Psychotic illness • Rett: Stereotypic hand movements • Angelman: Puppet-like gait, attraction to water • 5p- (Cri du chat): Inappropriate laughter, cat-cry during infancy

  22. Causes of ID

  23. Causes of ID

  24. Causes of ID

  25. Causes of ID

  26. Down Syndrome • Trisomy 21 • 95% caused by non-disjunction • 88% maternal non-disjunction • 2-3% Robertsonian translocation • Long arm chromosome 21 attached to chromosome 14 • Not linked to maternal age • 1-2% Mosaic • Some cells have normal karyotype and others have trisomy 21

  27. Down Syndrome • Typical physical appearance • Congenital heart disease • Haematological malignancies • Thyroid disorder • Eye and hearing disorders • Gastrointestinal abnormalities • Average IQ 50

  28. Down Syndrome • Increased risk of Alzheimer’s type dementia • Increased risk of autism • Possible increased risk of depressive disorder • Conduct disorder in childhood

  29. Prader Willi syndrome • Results from failure of expression of paternally derived gene on chromosome 15 • 15q11-13 • Failure of maternally derived gene leads to Angelman syndrome

  30. PWS genetics • Interstitial deletions 70% • Uniparental disomy 25% • Imprinting centre defects <5% • Chromosomal translocations 1%

  31. Clinical features • Infant • Lethargy • Hypotonia • Poor feeding / failure to thrive • Childhood • Short stature • Hypogonadism • Hyperphagia and obesity

  32. Clinical features

  33. Psychosis and PWS • Case reports of cyclic affective disorders and psychosis • Boer et al (2002) Lancet • Identified all people with PWS in Oxford/Anglia • 25 adults with genetic confirmation of PWS • 15 had detailed psychiatric assessment

  34. Psychosis and PWS • Boer 2002 • 28% of adults with PWS have severe affective disorder + psychotic symptoms • 8% of adults with deletion • 62% of adults with uniparental disomy • Later study (Soni 2007)

  35. Medication in PWS • Those on antipsychotic or antidepressant medication significantly less likely to have relapse • Those on mood stabilising medication more likely to have a relapse • Sodium valproate & carbamazepine may not be effective for people with PWS • Mood stabilisers only used in more severe, relapsing conditions (BPAD)

  36. Diagnostic and Assessment Issues in ID

  37. Diagnostic Challenges in ID • ICD-10 assumes a certain level of cognitive / verbal ability • Level of ID important in assessment of possible mental health problems • Short, simple questions • Risk of suggestibility • Repeat and check answers • Use time anchors

  38. Diagnostic challenges in ID • Same range of psychopathology is not experienced in people with ID as general population • ICD/DCM weighted heavily towards verbal items and intellectually complex concepts (guilt, body image etc.)

  39. Diagnostic Challenges in ID • Darren is a 35 year old man with severe intellectual disability and longstanding self-injurious behaviour (hand biting and banging his head against walls). He is taken to the GP due to increased self injurious behaviour. The GP starts risperidone and refers him to the LD psychiatrist due to his behaviour.

  40. Diagnostic Challenges • Diagnostic overshadowing:- behaviour / presentation is attributed to ID rather than a diagnosable condition • Baseline exaggeration :- high levels of unusual behaviour prior to the onset of a condition make it difficult to recognise the onset of a new disorder • Loss of skills and impairment of communication may also be signs of mental illness

  41. Diagnostic Challenges in ID • Mike is a 48 year old man with moderate learning disabilities. He is referred to the psychiatrist after being seen outside his new home waving at passing cars and making gestures. His support staff are concerned about him talking to himself and think he might have developed psychosis.

  42. Impact of ID on MH presentations • Psychosocial masking • Impoverished social skills and life experiences result in unsophisticated presentation of a disorder or misdiagnosis of unusual behaviour as a psychiatric disorder • Cognitive disintegration • Decreased ability to tolerate stress leading to anxiety-induced decompensation (often misdiagnosed as a psychotic illness) • Misdiagnosis of developmentally appropriate phenomenon • Developmentally appropriate behaviours that are inappropriate for chronological age are misdiagnosed as psychiatric disorder (solitary play, talking to oneself and imaginary friends taken as evidence of psychosis)

  43. Impact of functional impairment on mental health presentations • Implications for mental state examination • Assessment of decline in abilities • Working with carers • Sensory impairments • Common (deafness 40 x more common and blindness 8.5 x more common than general population)

  44. Diagnostic classificatory systems • DC-LD • Provides operationalised diagnostic criteria for psychiatric disorders in people with ID • Works in a complementary way with ICD-10 • Developed by the RCPsych • Hierarchical system to reach diagnoses

  45. DC-LD

  46. Example of DC-LD hierarchical approach • Jane is a 24 year old lady with moderate ID and excessive over eating • Use the hierarchical approach to consider the differential diagnosis

  47. Example of DC-LD hierarchical approach • Jane is a 24 year old lady with moderate ID and excessive over eating • Axis I: level of ID does not account for the over eating • Axis II: ascertain cause of ID. If Prader-Willi syndrome present then eating a feature of this. If not continue to Axis III • Axis III: • Level A: does Jane have a developmental disorder? Eg. is the over-eating a ritual associated with autism? • Level B: is there evidence of a psychiatric illness (e.g. depression or an eating disorder) • Level C: is a personality disorder present? Does this account for her over-eating?

  48. Summary • ID is defined as a significant impairment in cognitive abilities and adaptive social functioning that arises during the developmental period • Increased risk of physical and mental disorders • The cause of ID can shed light on MH presentation • Assessment must include consideration of the biological, psychological, social and developmental issues • The DC-LD provides a hierarchical structure to reach psychiatric diagnoses in people with ID

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