Excess activity and deficits in attention, behaviour regulation and impulse control are characterised differently by the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM) and the World Health Organization’s International Statistical Classification of Diseases and Related Health Problems (ICD). The 4th and 5th Editions of the DSM (DSM-IV and DSM-5TM) classify this condition as ADHD, whereas the 10th Revision of the ICD (ICD-10) characterises this as hyperkinetic disorder (HKD) (Andrews at al. 1999; World Health Organization 2001; American Psychiatric Association 2013). Although both classification systems use similar behavioural criteria, they differ in diagnostic decisions, and comparison studies suggest that HKD is associated with greater severity than ADHD. Using data from the Multimodal Treatment of ADHD (MTA) study,* the long-term outcomes of children with a baseline diagnosis of HKD according to the ICD-10 were assessed.
The research criteria for HKD were utilised by applying HYPESCHEME† filters to baseline ratings from the Diagnostic Interview Schedule for Children (DISC)–Parent Interview and the Swanson, Nolan and Pelham (SNAP) Teacher Rating Scale; self- and parent-reports from the youth adult version of the DISC (DISC-YA) were used to determine adult HKD. To determine adult ADHD symptomatology at 12-, 14- and 16-year follow-ups, both the self- and parent-rated Conners’ Adult ADHD Rating Scale (CAARS) and the DISC-YA were used. Substance use, educational outcomes, occupational, emotional and socioeconomic functioning, sexual behaviour, justice involvement, medication use, impairment, height and car crashes were also assessed.
The original MTA study included 579 children with a diagnosis of combined-type ADHD. According to the ICD-10, 145 of these children met the criteria for HKD (“original HKD”), and in 109 children, this continued into adulthood. On the other hand, 434 children were identified as not having HKD, and this was also true in 367 of these children in adulthood. In the authors’ analyses, they also included individuals who had generalised anxiety disorder (GAD)/depression. In this instance, a total of 178 of the 579 children in the MTA study were characterised as having HKD (“expanded HKD”) according to the ICD-10, which continued into adulthood for most of these children (n=135); however 401 children did not have HKD and it was not present in adulthood for 341 of these children.
A comparison of children with and without HKD (n=109 versus n=367) from the “original HKD” sample showed that according to the DSM-IV and DSM-5TM, there were no differences in the severity of symptoms (p>0.05) or persistence of adult ADHD (p>0.05). This was also observed in the “expanded HKD” sample (n=135 versus n=341). The use of stimulants and rates of consistent medication use were comparable between all groups; however, children with comorbid anxiety or depression (analysed using the “expanded HKD” sample) were more likely to demonstrate symptoms of ADHD in adulthood (p<0.005). There were no major differences in adult functional outcomes in the “original HKD” group compared with those without HKD; however, emotional lability problems (mean 0.86 [standard deviation (SD) 0.47] versus mean 0.94 [SD 0.57]; p=0.005) and car accidents (mean 50 [SD 38.75] versus mean 209 [SD 53.58]; p=0.032) were more common in those without HKD, whereas job losses (mean 1.28 [SD 1.68] versus mean 1.09 [SD 1.4]; p=0.01) were higher in those in the “original HKD” group. Conversely, in the “expanded HKD” group, individuals with HKD were at a lower risk for car accidents (mean 60 [SD 38.5] versus mean 199 [SD 54.8]; p=0.006) and emotional lability (mean 0.89 [SD 0.49] versus mean 0.93 [SD 0.57]; p=0.003) than those without HKD, and there were no differences in job losses (mean 1.19 [SD 1.6] versus mean 1.11 [SD 1.43]; p=0.09) or use of stimulants (mean 19.3 [SD 20.63] versus mean 16.1 [SD 19.04]; p=0.17). Patterns of medication use throughout adolescence, stimulant use in adulthood, adult symptom severity, substance use, educational outcomes, socioeconomic functioning, sexual behaviour, justice involvement and height were not significantly different between groups (p>0.05); however, individuals in the “original HKD” group reported higher medication use than those without HKD (mean 20.3 [SD 21.21] versus mean 16.05 [SD 18.95]; p=0.08). Using the HYPESCHEME filters, 6/109 (5.5%) children in the “original HKD” group and 12/135 (8.9%) children in the “expanded HKD” group could be classified as having HKD in adulthood according to the ICD-10 criteria.
The authors indicated that a limitation of this study was that compared with those without HKD, individuals identified at baseline as having HKD had a higher rate of attrition. They stated that the apparent outcome of HKD relative to ADHD without HKD would be artificially improved if the most severe cases were lost to follow-up.
The authors concluded that despite their initial hypothesis, children from the MTA study who displayed a greater initial symptom severity and pervasiveness with an ICD-10 diagnosis of HKD at baseline did not have worse outcomes in young adulthood compared with those who did not meet the criteria for HKD.
*In brief, the MTA study included 579 children aged between 7 and 9 years old with a diagnosis of combined-type ADHD according to DSM-IV criteria. Individuals were randomly assigned to systematic medication management, comprehensive multicomponent behavioural treatment or a combination of both. Study treatment was provided for 14 months, and assessment occurred at 24 months, 36 months, and 6, 8, 10, 12, 14 and 16 years after baseline. A total of 476 (82.2%) of the original 579 children also had assessments in adulthood
†HYPESCHEME can generate an explicit category of HKD and ADHD as it is an algorithm used for coding information from a variety of different records and instruments. The HYPESCHEME applied filters relating to comorbidity, symptom domain, pervasiveness and impairment
Arnold LE, Roy A, Taylor E, et al. Predictive utility of childhood diagnosis of ICD-10 hyperkinetic disorder: adult outcomes in the MTA and effect of comorbidity. Eur Child Adolesc Psychiatry 2018; Epub ahead of print.
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World Health Organization. International Classification of Functioning, Disability and Health: ICF. World Health Organization 2001, Geneva.
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (DSM-5®). American Psychiatric Pub 2013, Washington DC.