Current theoretical & practical issues in autism diagnosis

1. Current theoretical & practical issues in autism diagnosis Dr. Elizabeth Sheppard Developmental Cognitive Neuropsychology (C8CLDC) Child Clinical Neuropsychology (C8DCHN)

2. Objectives • Provide background information on autism and ASD • Discuss conceptual issues surrounding diagnosis of autism • Discuss approach to possible causes of behavioural symptoms of autism • Discuss current thinking & future challenges on changing prevalence of ASD

3. Childhood disorders • Acquired – through damage to brain • Developmental - no evidence of neurological injury – abnormal cognitive development i.e. deviant developmental path • May be influenced by various factors • Genetics • Physiology • Environment

4. What is autism? • Autism is characterised by social & non-social features: • Social features regarded as ‘triad of impairments’ (Wing & Gould, 1979) in socialisation, imagination & communication • Non-social features – narrow range of interests, repetitive behaviour, good performance on visuospatial tasks, savant skills • Current thinking aims to explain a triad of impairments in social interaction, communication, & restricted & repetitive interests (DSM-IV, APA, 1994)

5. Autism & Asperger Syndrome • Autism first described by Kanner (1943) & Asperger (1944) • Asperger focused more on children who were intellectually able – Wing (1981) – ‘Asperger Syndrome’ – subgroup of autism • Asperger differ from autism • More intellectually able – must have IQ>70 • Language onset not delayed • Motor impairments? • Age of onset? • Still controversial - HFA?

6. The Autism Spectrum • Autistic spectrum (Wing & Gould, 1979) - autism, Asperger Syndrome, atypical autism & PDD-not otherwise specified (plus Rett’s syndrome & Fragile X) • These known as autism spectrum disorders (or pervasive developmental disorders) • Individuals who gain a diagnosis of ASD (PDD-NOS) may have greater symptomology in some areas than others, mild impairments in several areas or late onset

7. Is there a single cause for autistic symptomology? • Research on autism has been geared towards explaining triad of impairments (socialisation, communication, restricted interests) by a single cause • ASD diagnosis requires all three impairments to be present – but do they necessarily co-occur? • Ronald et al. (2006) investigated autistic-like traits in general population (no diagnosis) • Looked at correlations between social, communication impairments, & restricted interests

8. Is there a single cause for autistic symptomology? • Low-to-modest correlations in 3 core areas: • Social & communication r=0.2-0.4 • Communication & restricted behaviour r=0.3-0.4 • Social & restricted behaviour r=0.1-0.3 • Considerable number of children showed impairments in just one area: • 59% those with social impairments, only had social impairments • 10% all children had one impairment only • This implies there are 3 dimensions of impairment that are relatively independent

9. Is there a single cause for autistic symptomology? Social impairments Communication impairments Autism Restricted interests Just language difficulties = pragmatic language impairment Language + social difficulties =PDD-NOS (or atypical autism)

10. Is there a single cause for autistic symptomology? • Genetic evidence • Twin studies suggest each aspect of triad highly heritable • However, most genetic effects are specific - act on just one part of triad (Ronald et al., 2006) • Family studies investigating broader phenotype (subclinical manifestations) often find relatives showing only isolated traits (e.g. Piven et al., 1997)

11. Is there a single cause for autistic symptomology? • If these dimensions independent, may explain heterogeneity observable in populations with autism (Happé et al., 2006) • May also be individuals with isolated impairments in one part of triad who fit no diagnosis at present – need to meet their needs in future – first step may be to start measuring the three aspects of the triad separately • Impact on research at cognitive, biological & genetic levels & for treatment

12. Prevalence of autism • Prevalence of autism first estimated at 0.4/1000 (Lotter, 1966) • More recent studies estimate autism rates as 2-4/1000; and 6-7/1000 for all ASDs (Baird et al., 2000; Bertrand et al., 2001; Chakrabarti & Fombonne, 2001) • 10-fold increase? • So is autism increasing within the population?

13. Prevalence of autism • Possible reasons for increase 1)Increase is real – need to explain why. Introduction of the MMR vaccine? No research supports temporal association (e.g. Dales et al., 2001) & no plausible causal explanation (e.g. Halsey et al., 2001) 2) Artefacts producing false positive diagnosis e.g. overexpansion of diagnostic category – hard to prove as no litmus test (genetic marker)

14. Prevalence of autism • Possible reasons for increase 3) The current rate is correct but there has not been an increase – • diagnostic boundaries have changed • inclusion of spectrum • Increasing recognition of comorbidity (e.g. Downs, Tourette syndrome, cerebral palsy) • Improvements in case-finding methods • Populations sampled • Increased public awareness

15. Prevalence of autism • Concurrent decrease in children registered as having mental retardation (Croen et al., 2002) • Estimates of those with ASD with IQ>70 now 50-80% - implies rise in intellectually able individuals diagnosed • 70-90% those with ASD diagnoses were male

16. Prevalence of autism • How might we determine whether prevalence is increasing? • Cohort study – e.g. comparing 25-yr-olds & 40-yr-olds. But diagnosis less reliable in adults & sampling difficulties • Improve methods of measurement – this will be linked to our conceptualisation of ASDs • Prospective study of ‘at risk’ children e.g. siblings of those already diagnosed with autism (Wing & Potter, 2002) – but these may differ from individuals where genetic risk is lower

17. Summary • Autism is not a single condition but rather there is a spectrum of conditions • The core behavioural features observed in autism are actually relatively independent & each can be observed in isolation – related conditions (e.g. PLI) may reflect expression of just one of these features • Autism is apparently increasing in prevalence – this is likely due to advances in understanding/diagnosis rather than a true increase

18. References • American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th edn.). Washington DC: American Psychiatric Association. • Asperger, H. (1944). Die "Autistischen Psychopathen" im kindesalter. Archivfur Psychiatrie und Nervenkrankheiten, 117, 76-136. • Baird, G., Charman, T., Baron-Cohen, S., Swettenham, J., Wheelwright, S., & Drew, A. (2000). A screening instrument for autism at 18 months of age: a siex-year follow-up study. Journal of the American Academy of Child and Adolescent Psychiatry, 39, 694-702. • Bertrand, J., Mars, A., Boyle, C., Bove, F., Yeargin-Allsopp, M., & Decoufle, P. (2001). Prevalence of autism in a United States population: The Brick Township, New Jersey, investigation. Pediatrics, 108, 1155-1161. • Bishop, D. V. M., & Norbury, C. F. (2002). Exploring the borderlands of autistic disorder and specific language impairment: a study using standardised diagnostic instruments. Journal of Child Psychology and Psychiatry, 43, 917-929. • Chakrabarti, S. & Fombonne, E. (2001). Pervasive developmental disorders in preschool children. Journal of the American Medical Association, 285, 3093-3099. • Charman, T. (2002). The prevalence of autism spectrum disorders: recent evidence and future challenges. European Journal of Child & Adolescent Psychiatry, 11, 249-256. • Croen, L., Grether, J., & Hoogstrate, J. (2002). The changing prevalence of autism in California. Journal of Autism and Developmental Disorders, 32, 207-215. • Dales, L., Hammer, S. J., & Smith, N. J. (2001). Time trends in autism and MMR immunization coverage in California. Journal of the American Medical Association, 285, 1183-1185.

19. References • Halsey, N. A., Hyman, S. L. & the Conference Writing Panel (2001). Measles-mumps-rubella vaccine and autism spectrum disorders: report from the new challenges in childhood immunizations conference convened in Oak Brook, Illinois, June 12-13, 2000. Pediatrics, 107, e84. • Happé, F., Ronald, A., & Plomin, R. (2006). Time to give up on a single explanation for autism. Nature Neuroscience, 9, 1218-1220 • Kanner, L. (1943). Autistic disturbance of affective contact. Nervous Child, 2, 217-250. Reprinted in L. Kanner (1973). Childhood psychosis: Initial studies and new insights. New York: John Wiley & Sons. • Lotter, V. (1966). Epidemiology of autistic conditions in young children. Social Psychiatry, 1, 124-137. • Piven, J., Palmer, P., Jacobi, D., Childress, D., & Arndt, S. (1997). Broader autism phenotype: Evidence from a family history of multiple-incidence autism families. American Journal of Psychiatry, 154, 185-190. • Ronald, A. et al. (2006). Genetic heterogeniety between the three components of the autism spectrum: A twin study. Journal of the American Academy of Child & Adolescent Psychiatry, 45, 691-699. • Wing, L. (1981). Asperger's syndrome: A clinical account. Psychological Medicine, 11, 115-129. • Wing, L., & Gould, J. (1979). Severe impairments of social interaction and associated abnormalities in children: Epidemiology and classification. Journal of Autism and Developmental Disorders, 9, 11-29. • Wing, L., & Potter, D. (2002). The epidemiology of autistic spectrum disorders: Is the prevalence rising? Mental Retardation and Developmental Disabilities Reviews, 8, 151-161.

20. Autism: A Disorder of Executive Function? Dr. Elizabeth Sheppard Developmental Cognitive Neuropsychology (C8CLDC) Child Clinical Neuropsychology (C8DCHN)

21. Objectives • Discuss evidence for autism as disorder of EF • Evidence comes from: • Behavioural evidence • Cognitive testing – is performance normal on tasks that involve one or more EF? • Biological studies – what brain regions are implicated? • Talk about problems with EF account of autism

22. Neuropsychological Studies • The goal of neuropsychological studies is to establish the primary deficit in each disorder. • A PRIMARY deficit needs to: • Be universal • Be specific (Discriminant validity) • Be necessary and sufficient to cause symptoms of the disorder

23. Is autism a disorder of executive function? • Major proponents – Russell, Ozonoff etc. • This view argues that ED underlies many of the key features of ASD especially rigidity & perseveration • These caused by difficulties initiating new non-routine actions & tendency to be stuck in given task set • Strong liking for repetitive behaviour & elaborate rituals – benefit from prompts & externally provided structures which initiate routines or help to switch set

24. Cognitive evidence of EF deficits in autism Stimulus overselectivity – tendency to respond only to a subset of environmental cues which are often irrelevant (Lovaas et al., 1979). Perseveration– continue to respond to only one stimulus dimension even after hundreds of trials which were not rewarded.(Koegel & Schreibman, 1977; Boucher,1977) Strict rule adherence - sequencing stimuli (Frith,1972; Boucher, 1977)

25. Cognitive evidence of EF deficits in autism • Planning – Deficits generally found on planning as indexed by Tower of Hanoi (e.g. Ozonoff et al., 1991) • Mental flexibility – often assessed with WCST – individuals with autism show deficits when necessary to shift response set i.e. perseverate (e.g. Prior & Hoffman, 1990)

26. Cognitive evidence of EF deficits in autism • Inhibition – individuals with autism appear unimpaired on measures e.g. Stroop task. • But show difficulties on Russell’s ‘windows task’ (e.g. Hughes & Russell, 1993). Russell argues individuals with autism fail tests of EF if no clear rationale

27. Cognitive evidence of EF deficits in autism • Generativity – capacity to generate novel ideas & behaviours spontaneously • Lewis & Boucher (1991) – drawings of children with autism showed greater degree of thematic relatedness • Boucher (1988) – children with autism deficits in producing miscellaneous words • Jarrold et al. (1996) – impairment in spontaneous production of pretence • Working memory – Bennetto et al. – individuals with autism impaired in tests of working memory but not other types of memory. But Geurts et al. (2004)found no working memory deficits in autism

28. Cognitive evidence of EF deficits in autism • Review of studies - Pennington and Ozonoff (1996) • 13/14 studies found deficits in autism on at least one measure of EF • Found those with autism poorer than comparison participants on 25/32 (78%) tasks used across studies • Hill (2004) – another review of studies – concluded widespread impairments in planning & perseveration in autism, but perhaps not inhibition

29. Primacy of EF deficits • Some argue EF allows TOM to develop (e.g. Ozonoff, 1997) – others say capacity to represent mental states needed for EF (e.g. Perner, 1998) • EF deficits in high and low ability individuals with autism but not TOM (Ozonoff et al., 1991) • Correlations between EF and TOM performance and EF predicts TOM better than vice versa (Hughes, 1998) • But TOM tasks may also have exec component - complex

30. Biological evidence for Ex Dysfunction in autism • More evidence for functional abnormalities than structural abnormalities. • Structural/neuroanatomical - some abnormalities found in the : • limbic system (Bauman & Kemper, 1985) • Cerebellum (Bauman & Kemper, 1988) • parietal lobes (Courchesne et al., 1988) • temporal lobes (Hetzler & Griffin, 1981) • ventricle system (Gaffney et al., 1989) • orbitofrontal cortex (Salmond et al., 2003) • But little evidence for structural abnormalities in PFC

31. Biological evidence for Ex Dysfunction in autism • Indirect link between frontal function & ED • Some argue ED is consequence of medial temporal lobe functional abnormalities • Impairments in prefrontal function seen as consequence of this – differences arise from severity of abnormality (e.g. Ohnishi et al., 2000) • Consequences only become apparent when frontal lobes mature

32. Biological evidence for Ex Dysfunction in autism • Direct link between frontal lobe function & ED • Dysfunctional integration of frontal lobes with rest of brain/ abnormal development in neuronal sophistication/ abnormal myelinisation • Findings of delayed postnatal maturation of frontal lobes (Zilbovicius et al, 1995) & reduced functional connectivity of frontal cortex with other cortical & subcortical regions supports this (Luna et al., 2002)

33. Koshino et al. (2005) – group with autism showed reduced activation in left dorsolateral prefrontal cortex during working memory task Biological evidence for Ex Dysfunction in autism • SPECT, PET, EEG studies show evidence of unusual function in the frontal areas in individuals with ASD (George et al., 1992; Horwitz et al., 1988; Dawson et al., 1993)

34. Biological evidence for Ex Dysfunction in autism • Broader phenotype studies – investigate presence of autistic features in relatives of those with condition • Deficits in planning & mental flexibility characterise broader phenotype (e.g. Hughes et al., 1997)

35. Problems for the EF account of autism • Although there are similarities between autism & children with acquired frontal lesions, they aren’t the same • Question over universality – some studies have not identified deficits in participants e.g. Minshew et al., 1992 • Specificity – ED & frontal metaphor used for other developmental disorders e.g. Tourette syndrome, ADHD – characteristics of these different from autism. Need to explain this (more next week!)

36. Summary • Evidence for autism as executive disorder at cognitive & biological levels • Deficits in planning & mental flexibility • Frontal lobe abnormalities • Questions over primacy, universality & specificity of EF deficits in autism

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