Hyperkinetic disorders in childhood: epidemiology, etiology, clinical features, course, and treatment

01Definition and overview

A hyperkinetic disorder is a persistent pattern of inattention, overactivity and impulsivity, out of keeping with the child's age and developmental level, that starts early, shows in more than one setting and impairs the child's life. It is ICD-10's narrower version of what DSM-5 and ICD-11 call attention deficit hyperactivity disorder (ADHD).

ICD-11 (6A05) follows DSM-5: ADHD with predominantly inattentive, predominantly hyperactive-impulsive or combined presentations, with onset usually before 12, and it no longer excludes autism. Most European countries still code with ICD-10, so a child diagnosed with ADHD may or may not meet the stricter ICD-10 criteria. UK guidance asks for the DSM-5 or ICD-11 criteria and advises against excluding the diagnosis because of autism.

02Etiology and pathophysiology

ADHD has no single cause. It is a neurodevelopmental disorder in which many genes of small effect, and some environmental risks, shift the development of brain systems for attention, inhibition and reward.

The core changes are in fronto-striatal and fronto-cerebellar circuits regulated by dopamine and noradrenaline: weaker inhibitory control and working memory, and a preference for small immediate rewards over larger delayed ones. Imaging shows a cortex that matures a few years later than usual, most clearly in prefrontal regions, and slightly smaller brain volumes on average, though no scan diagnoses ADHD. The drugs act on the same systems: stimulants raise dopamine and noradrenaline at the synapse by blocking the dopamine transporter and the noradrenaline transporter, and amphetamines also release them.

03Clinical features

The picture changes with age. Preschool children show relentless overactivity and accidents; school-age children show classroom problems, poor schoolwork and conflict with peers; adolescents feel inner restlessness rather than running about, and take risks with driving, sex and substances; adults struggle with disorganisation, lateness, forgetfulness, emotional volatility and unstable work and relationships. Girls more often have inattentive symptoms, attract less attention and are diagnosed later.

Comorbidity is the rule, with half to four-fifths having at least one other condition:

• oppositional defiant disorder and conduct disorder;
• specific learning disorders such as dyslexia, and developmental coordination disorder;
• autism, tics and Tourette syndrome;
• anxiety, depression and emotional dysregulation;
• sleep problems;
• in adolescence and adult life, substance misuse and, in some, antisocial personality disorder.

The consequences are real: academic underachievement and exclusion from school, injuries and road accidents, early pregnancy, unemployment, criminal convictions and a roughly doubled mortality, mostly from accidents.

04Diagnosis and management

Assessment

1. 1

   Referral

   A child with suspected ADHD is assessed by a specialist, a child psychiatrist or paediatrician with training in ADHD; in the UK a GP does not diagnose it or start medication.
2. 2

   History

   From parents and child: onset, course, settings, development, family history, sleep, and the impact at home and school; from school: teacher reports and examples of work.
3. 3

   Observation

   In clinic and, if possible, at school; rating scales such as the Conners rating scales, SNAP-IV or the Strengths and Difficulties Questionnaire, completed by parents and teachers.
4. 4

   Examination

   Growth, heart rate and blood pressure, cardiovascular examination, hearing and vision, a neurological examination and a look for dysmorphic features.
5. 5

   Diagnosis

   Made when the criteria are met with at least moderate impairment in more than one setting, and other explanations have been considered.

Rating scales support but do not make the diagnosis. Blood tests, an EEG and brain imaging are not routine, but are done when the history suggests a medical cause.

Treatment

Every family gets information about ADHD, support, and advice on changes at home and school: clear routines, short tasks broken into steps, immediate praise and rewards, seating near the teacher and away from distraction, movement breaks, and a written plan shared between home and school. Treatment then depends on age, as UK guidance sets out:

1. 1

   Under 5

   An ADHD-focused group parent-training programme first. Medication only after a second specialist opinion from a service experienced with young children.
2. 2

   5 and over

   If symptoms still cause significant impairment after the environmental changes, methylphenidate is first-line, short- or long-acting. Parent training is added if there is oppositional or conduct disorder; CBT can help adolescents who are on medication but still impaired.
3. 3

   Second line

   After a 6-week trial of methylphenidate at an adequate dose without enough benefit, lisdexamfetamine; dexamfetamine if lisdexamfetamine helps but its long action is not tolerated.
4. 4

   Third line

   If neither stimulant works or is tolerated, atomoxetine or guanfacine.
5. 5

   Adults

   Lisdexamfetamine or methylphenidate first-line, atomoxetine if neither works or is tolerated, with psychological support for those who prefer not to take medication or still struggle.

Stimulants are the most effective treatment in the short term, helping about 70 per cent of children. Their common side effects are loss of appetite and weight, trouble getting to sleep, headache, stomach ache, irritability, anxiety and a small rise in heart rate and blood pressure. Rarer are tics, psychotic symptoms and mania. They are used with caution in heart disease, hypertension, a history of psychosis or substance misuse, and not with a monoamine oxidase inhibitor. Clonidine is used off-label, mainly with tics or sleep problems and in the UK only on the advice of a tertiary ADHD service; antipsychotics do not treat ADHD.

Before and during medication

Before starting, the specialist records the history (fainting or breathlessness on exertion, palpitations, chest pain, a family history of sudden cardiac death under 40), height and weight on a growth chart, heart rate and blood pressure on a centile chart, and examines the heart. An ECG is not routine, but is done, and a cardiologist's opinion sought, when the history or examination suggests heart disease, or with drugs that affect the QT interval.

Shared care with the GP is common once the dose is stable, with the specialist reviewing at least yearly.

Diversion and misuse

Stimulants are controlled drugs. They are diverted to others, often fellow students, for studying, weight loss or recreation, and immediate-release tablets can be crushed and snorted or injected. The risk is highest in adolescents and young adults and in those with a history of substance misuse. It is reduced by choosing lisdexamfetamine or a long-acting methylphenidate, or a non-stimulant such as atomoxetine; by small supplies and a parent holding the medication for younger children; by talking about it openly; and by noticing early or "lost" prescriptions. Untreated ADHD itself raises the risk of substance misuse, and treatment does not.

05Epidemiology

of children meet DSM-5 criteria for ADHD

about 5per centof children meet DSM-5 criteria for ADHD

meet the stricter ICD-10 criteria for hyperkinetic disorder

1–2per centmeet the stricter ICD-10 criteria for hyperkinetic disorder

of adults have ADHD

2–3per centof adults have ADHD

Prevalence is similar across countries and continents when the same methods are used; apparent differences come from the criteria and the method. Boys are diagnosed two to three times as often as girls in the community and more often still in clinics, where inattentive girls are under-recognised; in adults the ratio is closer to equal. Diagnoses and prescriptions have risen steeply in the UK and much of Europe in the last decade, above all in adults and girls, with long waiting lists for assessment. ADHD is over-represented in prisons and among people with substance misuse.

06Prognosis

Overactivity and impulsivity decline through adolescence, but inattention often persists. In follow-up studies, about 15 per cent of children with ADHD still meet the full criteria at 25, and about two-thirds still have impairing symptoms. A worse course is associated with comorbid conduct disorder, as in ICD-10's hyperkinetic conduct disorder, low IQ, family adversity and parental mental illness.

Treatment changes the outlook. In Swedish registers, periods on ADHD medication were associated with about a third fewer criminal convictions in men and two-fifths fewer in women, and with fewer injuries, road accidents and episodes of substance misuse; mortality in ADHD, roughly double the general population's, is mostly from accidents. Stimulants slow growth a little: in one long follow-up, children who kept taking them through childhood were about 2.5 cm shorter as young adults than those who took little, so height is monitored and breaks from treatment are considered when growth falters. Adults with ADHD benefit from treatment as children do, and transition from children's to adult services is planned rather than letting treatment lapse at 18.