This article discusses the relationship of maturation to ADHD and hyperkinetic disorder (HKD), with an emphasis on current research in ADHD and HKD, persistence and remission of ADHD symptoms over time and brain maturational trajectories. Conclusion: ADHD is a broad, heterogeneous syndrome and only a subgroup of subjects has a diagnosis of HKD, which is a subset of individuals with severe ADHD combined subtype. Children showing symptoms above the threshold for a diagnosis of ADHD are at risk of developing comorbid conditions and increasing stress in both parents and teachers. In some subjects, ADHD symptoms can improve over time during maturation and development. These children with a diagnosis of ADHD could be viewed as showing variants of normal childhood behaviour with maturational trajectories that are lagging behind but will catch up. ADHD could therefore represent a continuum from normality at one extreme to a severe disorder, HKD according to ICD‐10, at the other extreme.

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Attention deficit hyperactivity disorder (ADHD) has been shown to be substantially influenced by genetic factors. However it is still not known how these effects are mediated. The aim of this study is to evaluate whether genetic disposition for global maturity could be a mediator of the well-known findings of genetic factors for ADHD symptoms. A total of 1480 pairs of twins aged 8-9 years were identified through the population-based Swedish Twin Registry. A mailed questionnaire with items from DSM-III-R for ADHD and items concerning global maturity were completed by the parents. The results showed that global maturity mediated part of genetic effects for ADHD for both boys and girls. There were also genetic, shared environmental, as well as nonshared environmental effects unique to ADHD not in common with global maturity. Thus, there are at least two pathways through which genetic effects can influence ADHD: one through predisposition for maturational lag and one unique to ADHD, possibly mediated by personality. The results indicate that maturational lag could be of importance for treatment and prognosis of ADHD.

The Gordon Diagnostic System (GDS) is a portable easily operated computerized tool developed to measure impulse control, attention and vigilance. In 1988, it was standardized for use among American children. The aim of this study was to evaluate the GDS for use among Swedish children. A clinical sample of 71 Swedish children, mean age 10.5 y, fulfilling the ADHD criteria according to the DSM‐IV was compared with a control sample of 88 children, mean age 10.2 y, with no known psychiatric diagnosis. The clinical sample showed lower GDS scores in all age groups, with some exceptions. The GDS scores were not associated with gender, but strongly associated with age, especially in the control sample. The accuracy of the GDS referring a specific child to either of the samples was, as expected, not impressive. With respect to the practical usefulness, the GDS was well accepted by the children and parents in both samples. The findings in age variation and when comparing children with ADHD and controls are in agreement with results from other studies.

Larsson J-O, Lichtenstein P, Fried I, El-Sayed E, Rydelius PA. Parents' perception of mental development and behavioural problems in 8 to 9-year-old children. Acta Paediatr 2000; 89: 1469-73. Stockholm. ISSN 0803-5253A slow maturational rate may be an underlying antecedent of a psychiatric disorder. If this is correct, differences in behavioural problems could be related to the maturity level in children of the same chronological age. The aim of the study was to compare the parents' perceptions and assessments of their children's maturational status and behavioural problems. A population based on a nationwide sample from the Swedish twin-register of 8 to 9-y-old children (n = 1079) was used. The parents completed a questionnaire including their views on their child's maturity level, the Swedish version of the Child Behaviour Checklist (CBCL) and an Attention De cit Hyperactivity Disorder (ADHD) checklist based on the DSM-III-R criteria. Multivariate analyses showed a statistically signi cant relationship between immaturity reported by the parents and several behavioural problems reported on the CBCL: somatic complaints, anxious and depressed, social problems, thought problems, attention problems, behaviour problems and aggressive behaviour. There was also a statistically signi cant relationship between the maturity factor and the CBCL grouping of syndromes (internalizing, externalizing, total behaviour problems score) as well as between the maturity factor and ADHD. Conclusion:We conclude that at least from the parents' point of view the behaviour problems in their children may be related to maturity.