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Motor problems, often characterised as clumsiness or poor motor coordination, have been …

Biology Articles » Neurobiology » Cognitive Neurobiology » Fine motor skills in South African children with symptoms of ADHD: influence of subtype, gender, age, and hand dominance » Background

- Fine motor skills in South African children with symptoms of ADHD: influence of subtype, gender, age, and hand dominance

Attention-Deficit/Hyperactivity Disorder (ADHD) is a prevalent, heterogeneous, and debilitating neurodevelopmental disorder with an early onset. The disorder consists of a persistent pattern of inattentiveness, impulsiveness, and/or hyperactivity that is inconsistent with the child's developmental level [1]. ADHD is the most common child psychiatric disorder in Europe and the United States, affecting 3–10% of primary school children [2-4]. The disorder is generally more prevalent in males, but more severe in females [5]. Male-to-female ratios vary from 9:1 to 6:1 in clinic-referred samples, but is only approximately 3:1 in population-based ones [3]. ADHD is associated with proneness for repeated accidents, depressive and anxiety disorders, learning disabilities, and school failure [4,6-9]. The disorder is also associated with later increased incidence of substance abuse if not diagnosed and treated at an early age [10]. Thus, the economic, educational, social, and personal costs of ADHD are enormous.

Although referral practices and assessment procedures are neither well developed nor standardized in developing countries [11], ADHD is as prevalent and has the same sex ratios on the African continent as in Western countries [12-14] suggesting that ADHD is caused by the same fundamental neurobiological factors probably hypofunctioning dopamine systems influencing among other functions learning and behavioural planning [15,16].

DSM-IV [1] identifies three subtypes of the disorder, namely: ADHD predominantly inattentive type (ADHD-PI) if six (or more) symptoms of inattention (but fewer than six symptoms of hyperactivity-impulsiveness) have persisted for at least 6 months; ADHD predominantly Hyperactive-Impulsive Type (ADHD-HI), if six (or more) symptoms of hyperactivity-impulsiveness (but fewer than six symptoms of inattention) have persisted for at least 6 months; and ADHD combined type (ADHD-C), if at least six symptoms of inattention and at least six symptoms of hyperactivity-impulsiveness have persisted for at least 6 months.

Besides the symptoms of inattention, hyperactivity, and impulsiveness, the ADHD child's motor ability is frequently significantly lower than would be expected of his age and level of intellectual functioning [1]. The wide range of motor problems include delays in achieving motor milestones, problems with movement planning and execution (reaction time, movement time, accuracy, and variability) [17], and parameter setting (not to be able to adapt their task performance to environmental requirements) [18]. Children with ADHD who experience motor problems often display deficits in requiring complex co-ordinations of movement, such as handwriting [2,18]. These problems may interfere with the ADHD child's daily functioning and influence their academic performance [19].

Development Coordination Disorder (DCD) is a disorder with marked impairment in the development of motor coordination which cannot be attributed to a general medical condition or mental retardation [1]. Although DSM-IV [1] does not link DCD with ADHD, the disorders co-occur in ~50% of cases [18,20,21] through a shared, additive genetic component between most subtypes of ADHD and DCD [22]. The children diagnosed with DCD who have problems with fine motor skills, are usually strongly linked to the ADHD-PI subtype [23]. In the Scandinavian countries the term DAMP (deficits in attention, motor control, and perception) is sometimes used for children with ADHD+DCD [8,24,25]. DAMP has been defined as a neurodevelopmental dysfunction syndrome with a high degree of comorbidity. Motor clumsiness is however, also associated with a variety of developmental disorders: learning disability [26], reading disorder [27], oppositional defiance disorder (ODD) [28] autism [17] and Asperger's syndrome [29,30].

The aspects of motor performance to be assessed in the present study were manual dexterity, complex coordination, and motor planning (by the Grooved Pegboard and the Maze Coordination Task), and manual dexterity (by the Finger Tapping Task).

The problems addressed were: Are motor problems associated with ADHD, also in African cultures? Are there differences in motor skills among the ADHD subtypes? Are there gender differences? Is there an effect of age? Are there differences in performance between the dominant and non-dominant hand?

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