Seminar 3 –
Characteristics and Comorbidity

Dido Green:
Guy’s Hospital, London

Co-morbid, Co-Existing, Co-occurring or Overlapping Conditions with Developmental Coordination Disorder (DCD)?

Analysis of the relationship between developmental conditions requires diagnostically distinct boundaries at both a theoretical and an empirical level. This paper will pose some questions which may throw some light on the singularity or complexity of DCD:

Criteria C and D of the DSMIV diagnostic criteria of DCD argue for the notion of a ‘specific’ motor problem in the absence of medical, psychiatric or learning difficulties. However, evidence favours a pluralistic construct. Rutter (1982) argued against the term ‘Minimal Brain Dysfunction’ (MBD) as there was no evidence of either brain damage or meaningfully distinctive symptoms in MBD that differed from psychiatric conditions, such as hyperkinetic disorder. More recently — and ironically — Whitmore and Bax (1997) refuted the term ‘Specific Learning Disorders’ due to the very lack of ‘specificity’ and defining features between conditions.

Further evidence of rather amorphous boundaries of developmental neuro-behavioural conditions is provided by the work of Weintraub and Mesulam (1983) and Rourke (1989) contrasting young patients with ‘Right hemispheric learning difficulties’, Asperger Syndrome (AS) and ‘Non-verbal Learning disabilities’. Green et al (2002) provided further weight to the pluralistic argument, which showed a strong overlap in the presentation of children with AS and DCD — not only of motor skills but also cognitive profile and gesture imitation as well as classroom behaviour (observed and/or reported by teachers and therapists from video recordings).

Cantwell (1996) introduces another point when considering co-morbidity (in his discussions of ADHD). Not only do co-morbid conditions and their prevalence rates differ across different types of samples (e.g. age bands, SES and geographic populations) but type and prevalence also depend on whether the sample is clinical or epidemiological and whether a clinical sample comes from community paediatric or child and adolescent health pathways. The former sample will frequently contain more children with learning disorders while in the latter, conduct disorders will be more prevalent.

Without undertaking systematic analysis, studies to date on DCD and over-lapping conditions suggest a higher prevalence of ADHD and DCD (60%, Rasmussen & Gillberg, 2000) and Specific Language Impairment and DCD (60%, Hill 1998 and Hill et al., 1998) in clinical samples; whereas samples arising from education or remedial learning centres show a high co-incidence of reading difficulties and DCD (55.5 %, Kaplan et al., 1998) as well as social, emotional and behaviour difficulties (82%, Losse et al., 1991). Cantwell (1996) further suggests that a particular association with a ‘co-morbid’ condition may identify subgroups of a condition (ADHD) which may differ in natural histories, underlying aetiological factors and/or responses to treatment.

Other than the research with Autistic Spectrum Disorders (ASD) — exploring different developmental trajectories of children with ASD and additional conditions such as Fragile X Syndrome, Tuberous Sclerosis, intellectual impairment or Semantic Pragmatic Disorder (Bishop, 1989; Bailey et al., 1991; Rutter, Bailey, Bolton, LeCouteur, 1994) — there are few studies contrasting any combined subtypes of DCD. Green, Sugden and Baird (2005, submitted) suggest that there is a high degree of overlap of DCD with emotional and behaviour disorders refuting the notion of singularity of co-ordination deficits in DCD. Furthermore, the degree of psychopathology did not correspond to age or extent of motor difficulty — implying a more primary and distinct association rather than any causal relationship — as has been implied in other studies (Skinner & Piek, 2001). Studies of subtypes within DCD are to date, exploratory and descriptive rather than contrasting of maturation or response to treatment.

Evidence for aetiological factors which may distinguish between developmental conditions is also scant. The prospective study of 29,889 children undertaken in US and reported by Nichols and Chen (1981) shows more than 10 demographic and maternal factors associated with poor coordination and neurological signs. These factors were not found to be exclusive to NS but may also predispose to hyperactivity or learning disabilities, rather the more early indicators (prenatal, neonatal or infancy) and early medical, developmental and social factors, the more likely the motor system will be negatively impacted.

Outstanding questions:

  1. Is the concept of specific developmental disorders defunct? Too little is known of the changing nature of DCD and/or changing impact on function or development;
  2. What are the comparative neuropsychological profiles of SDDs and PDDs? More similarities than differences are evident from neuropsychological studies;
  3. Are there behaviour distinctions between SDDs and PDDs? The clinical differences which define diagnostic cut-offs (via the extent of deficits such as social or attention problems) are not necessarily apparent on a daily basis but this may be dependent on the measures used for diagnoses;
  4. Are there distinct subtypes and variants within SDDs and PDDs? Remains a notional concept with little empirical evidence supporting different developmental trajectories when overall language and intellectual ability are taken into account;
  5. Can aetiological factors distinguish between SDDs and PDDs? Further studies of empirically collected data are required.

In summary: Without sufficient evidence to agree diagnostic distinctions between for example, a child with DCD who has some social difficulties versus the child with Asperger Syndrome who has poor co-ordination or the child with DCD and attention difficulties versus the child with ADHD and poor motor skills, the application of Criterion C cannot be even moderately adhered to. The removal of this criterion for diagnosis is recommended and replaced with a requirement to define the broader range of emotional and behavioural pathology associated for each child with DCD. This may provide clinical and research evidence of any ‘specific’ features that differentially contribute to developmental prospects and/or response to treatment.

Key References:

1. Attwood, T. (1998) Asperger’s Syndrome Jessica Kingsley Pubs., London

2. Bailey, A., Palferman, S., Heavey, L., LeCouteur, A. (1998) Autism: The phenotype in Relatives. Jour of Autism and Dev Disorders, 28 369-392.

3. Cantwell, D. (1996) Attention Deficit Disorder: A review of the past 10 years, AmAcad Child Adol Psychiatry, 35, 978-987

4. Green D, Baird G. (2005) DCD and Overlapping conditions, Chapter 5 in D. Sugden and M Chambers, Eds. (2005) Developmental Coordination Disorder, London: Whurr Pubs.

5. Green D, Sugden, D. Baird G. (submitted) A pilot study of psychopathology in Developmental Coordination Disorder, Child: Care, Health and Development

6. Green D, Baird G. et al (2002) The severity and nature of motor impairment in Asperger’s Syndrome: a comparison with Specific Developmental Disorder of Motor Function. Jour of Child Psych and Psych, 43 (5) 1-14.

7. Hill, E. (2001) Non-specific nature of specific language impairment: a review of the literature with regard to concomitant motor impairments. International Journal of Language & Communication Disorders, 36, 149-171.

8. Kaplan, B., Dewey, D., Crawford, S. & Wilson, B. (2001) The term Co-morbidity is of questionable value in reference to developmental disorders: Data and theory. Journal of Learning Disabilities, 34, 555-565.

9. Kaplan, B., Wilson, B., Dewey, D., & Crawford, S. (1998). DCD may not be a discrete disorder. Human Movement Science, 17, 471-490.

10. Klin, A., Volkmar, F.R., Sparrow, S.S., Cicchetti, D.V., & Rourke, B.P. (1995). Validity and neuropsychological characterization of Asperger’s syndrome: Convergence with Non-verbal Learning Disabilities syndrome. Journal of Child Psychology and psychiatry. Journal of Child Psychology and Psychiatry, 36, 1127-1139.

11. McAlonan, GM, Daly, E. et al (2002) Brain anatomy and sensorimotor gating in Asperger’s syndrome, BRAIN, 125, 1594-1606

12. McConaughy, S.H. & Achenbach, T.M. (1994). Comorbidity of Empirically based syndromes in matched general population and clinical samples. Journal of Child Psychology and Psychiatry, 35, 1141-1157.

13. Nichols, P.L., Chen, T-C. (1981) Minimal Brain Dysfunction A prospective study. New Jersey: Lawrence Erlbaum Ass, Pubs.

14. Rasmussen, P., Gillberg, C. (2000) Natural outcome of ADHD with Developmental Coordination Disorder at Age 22 Years: A controlled, longitudinal, community-based study. J of the American Academy of Child & Adolescent Psychiatry, 39, 1424-1431.

15. Rourke, B.P. (1989). Nonverbal learning disabilities: the syndrome and the model. New York: Guilford Press.

16. Rutter, M. (1982) Syndromes attributed to “Minimal Brain Dysfunction” in childhood. American Journal of Psychiatry, 139, 21-33.

17. Skinner, R.A., Piek, J.P. (2001). Psychosocial implications of poor motor

18. coordination in children and adolescents Human Movement Science, 20, 73-94.

19. Smith IM, Bryson SE (1998) Gesture Imitation in Autism: Nonsymbolic postures and sequences. Cognitive Neuropsychology 6/7/8/. 747-770

20. Szatmari P, Bartolucci G, Bremner R (1989) Asperger's Syndrome and Autism: Comparison of Early History and Outcome' Dev Med Child Neurology 31. 709-720

21. Weintraub S., Masulam M. (1963) Right Hemisphere Learning Disabilities. Arch Neurol. 40, 463-468.

22. Whitmore, K., & Bax, M. (1999). What do we mean by SLD? A Historical Perspective. In Whitmore, K., Hart H., and Willems G. (Eds). A Neurodevelopmental Approach to Specific Learning Disorders. (pp.1-23) Suffolk: MacKeith Press.

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