Emerging Evidence that AD/HD and DCD InteractMultiplicativelyChristopher Gillberg

Edmund Sonuga-Barke rightly draws attention to theneed for validation of a syndrome – any syndrome –beyond that of observing an association between twoconditions or symptoms. In the case of AD/HD andDCD, he highlights (i) the need to demonstrate a dis-tinctive profile of the DCD of AD/HD versus motorcoordination problems that might be present in otherpsychiatric disorders, and (ii) the requirement that co-occurring DCD and ADHD must interact multiplica-tively to produce significantly more severe problemsthan would be expected by just adding the problemsstemming from each condition.

Our studies were among the first to demonstrate anassociation of AD/HD with DCD (Kadesjo & Gillberg,1998) and of DCD with AD/HD (Kadesjo & Gillberg,1999). DCD has not been properly studied in otherchildhood onset behavioural/psychiatric conditions,with the possible exception of Asperger syndrome. So-nuga-Barke has a major point here, and it is clear thatthe study of motor incoordination and other neuro-motor problems in child psychiatric disorders generallyis an area in need of intensified systematic research inthe near future. It is interesting to note that in autismand Asperger syndrome, several recent studies suggestthe presence of both overall clumsiness (Gillberg, 1989;Ghaziuddin, Tsai, & Ghaziuddin, 1992) and more spe-cific motor dysfunction from infancy (Teitelbaum et al.,1998; Teitelbaum & Teitelbaum, 2003) in these condi-tions. Motor control problems may be important earlymarkers for a number of psychiatric disorders withearly childhood onset.

In respect of Sonuga-Barke’s suggestion that thesyndrome of DAMP would be better supported if therewere findings indicating a multiplicative interaction ofAD/HD and DCD, there is, in fact, growing evidence,including from the population study by Kadesjo andGillberg (1999), that AD/HD with DCD (i.e. DAMP) hasa strong interactive effect when it comes to predictinglearning problems and autistic symptoms. Opposi-tional-defiant disorder, on the other hand, is at a con-siderably lower rate in ADHD cases with comorbid DCDthan in those without. Indirect evidence for an inter-active effect between the two comes from the pro-spective follow-up study by our group in which childrenwith DAMP were shown to have a clear tendency formuch poorer outcome than those with AD/HD withoutDCD (Hellgren et al., 1994; Rasmussen & Gillberg,2000).

It may also be relevant to draw the reader’s attentionto the fact that the validity of hyperkinetic disorder vis-a-vis AD/HD does not have a lot of scientific support.Interestingly, the attention-deficit portion of AD/HDand the hyperactive-impulsive part of that disorder

show less pronounced overlap with each other than thatof AD/HD and DCD. Only slightly less than 20% of7-year-olds in the general population meeting at leastdiagnostic level number of inattention criteria for ADHDalso met at least diagnostic level number of criteria forhyperactivity (i.e. fulfilling symptom criteria for com-bined subtype ADHD). A similar degree of overlap wasseen when hyperactivity was taken as the starting point(data in Kadesjo & Gillberg, 1998). DCD and ADHD – onthe other hand – showed an almost 50% overlap in thesame study.

Possibly the only clear clinical conclusion regardingDAMP that can be drawn at the present time is thatmany children with DAMP are in need of specialist –including educational – intervention from early in life ifa psychosocially poor outcome is to be avoided. As agroup, they are probably in greater need of such inter-ventions than those with AD/HD without DCD, at leastin the areas of learning problems and autistic features.More research on whether or not DAMP is a subcategoryof AD/HD or a syndrome in its own right is needed.

ReferencesGhaziuddin, M., Tsai, L. Y., & Ghaziuddin, N. (1992). Brief

report: A reappraisal of clumsiness as a diagnostic feature ofAsperger syndrome. Journal of Autism and DevelopmentalDisorders, 22, 651–656.

Gillberg, C. (1989). Asperger syndrome in 23 Swedish children.Developmental Medicine and Child Neurology, 31, 520–531.

Hellgren, L., Gillberg, I. C., Bagenholm, A., & Gillberg, C.(1994). Children with deficits in attention, motor control andperception (DAMP) almost grown up: Psychiatric andpersonality disorders at age 16 years. Journal of ChildPsychology and Psychiatry, 35, 1255–1271.

Kadesjo, B., & Gillberg, C. (1998). Attention deficits andclumsiness in Swedish 7-year-old children. DevelopmentalMedicine and Child Neurology, 40, 796–811.

Kadesjo, B., & Gillberg, C. (1999). Developmental CoordinationDisorder in Swedish 7-year-old children. Journal of theAmerican Academy of Child and Adolescent Psychiatry, 38,820–828.

Rasmussen, P., & Gillberg, C. (2000). Natural outcome ofADHD with Developmental Coordination Disorder at age22 years: A controlled, longitudinal, community-basedstudy. Journal of the American Academy of Child andAdolescent Psychiatry, 39, 1424–1431.

Teitelbaum, P., Teitelbaum, O., Nye, J., Fryman, J., & Maurer,R. G. (1998). Movement analysis in infancy may be useful forearly diagnosis of autism. Proceedings of the NationalAcademy of Sciences of the United States of America, 95,13982–13987.

Teitelbaum, P., & Teitelbaum, O. (2003). EWMN revealsdisintegrated reflexes in Asperger’s syndrome in infancy. InThe social brain. Gothenburg, Sweden, March 25–27.

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