4.3 Hyperactivity and inattention
Hyperactive and inattentive behaviours are common in children, ranging in a continuum from normal behaviours, especially in young children, to developmentally inappropriate behaviours that impair daily activities at home and at school.
Developmentally inappropriate levels of hyperactivity and inattention may be the result of many factors, both intrinsic and environmental. These risk factors (Box 4.3.1) must all be considered in the assessment of children with difficult behaviour, especially when considering the diagnosis of attention-deficit/hyperactivity disorder (ADHD).
Definition of attention-deficit/hyperactivity disorder
ADHD is considered to be a developmental disorder of self-regulation, characterized by inattention and hyperactivity/impulsivity. The underlying neurobiological pathway involves the frontal–striatal–cerebellar networks, with deficits occurring in executive functioning, particularly response inhibition, vigilance, working memory and planning.
The diagnosis of ADHD is made using DSM-IV criteria. It is a descriptive diagnosis without implying cause, as it is not a discrete entity and has multiple causes. There must be developmentally inappropriate symptoms of inattention (Box 4.3.2) and/or hyperactivity/impulsivity (Box 4.3.3) with onset before 7 years of age, impairing social, academic or occupational functioning across multiple settings, and these symptoms are not a result of pervasive developmental disorder, psychosis or severe emotional disorders. Subtypes include mainly inattentive, mainly hyperactive or combined.
ADHD is common. The prevalence in the school-aged population generally is considered to be 3–5%. Boys are affected more commonly, particularly with hyperactivity. There is a higher incidence in disrupted families and in those with low incomes, again particularly with hyperactivity. There is a strong genetic factor, with about 30% of siblings, 25% of parents and 80% of identical twins affected. Molecular genetic studies have focused on chromosomes that regulate dopamine, the neurotransmitter most associated with learning, motivation, goals and movement, and noradrenaline (norepinephrine), involved in maintaining alertness and attention, particularly with novel stimuli. Two candidate genes, the dopamine transporter and dopamine receptor genes, are reported to be associated with ADHD.
Sammy, aged 6 years, was in his second year of school. His teacher complained that he never sat still, did not complete tasks, talked too much, interrupted, and was well behind with reading.
His mother recalled that he had been ‘on the go’ since about 2 years of age, always preferred playing outdoors rather than settling to games inside, never seemed to remember instructions or the house rules, and acted without thinking about the consequences. He hated homework and ‘often forgot’ to bring home his school reader.
Sammy’s problems are consistent with a diagnosis of ADHD and learning difficulties. Stimulant medication and consistent structure at home and at school helped his behavioural symptoms, but he also required educational assessment and specific reading support in the classroom.
Many children with ADHD have associated neurodevelopmental or mental health problems (co-morbidities) (Box 4.3.4). Because of overlapping features, separation into these diagnostic categories is complex; however, it is helpful when completing a descriptive assessment and recommending specific management programmes.
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