Attention Deficit Hyperactivity Disorder (ADHD)
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder. It affects approximately 3% to 5% of school-age children, meaning that in a class of 30, around one or two children may have ADHD.
It is estimated that more than 40,000 children in Hong Kong have ADHD, but only around 7,000 to 8,000 have been formally diagnosed. ADHD is more commonly diagnosed in boys, who are diagnosed approximately three to four times more often than girls. Its symptoms may change with age, although some may not completely disappear.
Research suggests that ADHD symptoms persist into adolescence and adulthood in approximately 65% of affected individuals. For more information, please see Adult ADHD.
Causes of ADHD
ADHD is associated with a combination of factors, including differences in brain structure and function, neurotransmitter activity, genetics and environmental influences. Parenting does not cause ADHD; however, the way a child is supported and guided may affect how their behaviours and symptoms are expressed and managed.
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Some studies suggest that, on average, children with ADHD may have a total brain volume approximately 3% to 5% smaller than that of children without ADHD, with differences particularly noticeable in the frontal and temporal lobes. The frontal lobes play an important role in attention and impulse control.
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ADHD is also associated with differences in neurotransmitter activity, particularly involving dopamine and noradrenaline. These differences may affect the brain’s ability to filter out distractions and regulate behaviour, contributing to symptoms such as inattention, hyperactivity and impulsivity.
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ADHD has a strong hereditary component. The estimated prevalence among children in the general population is approximately 3% to 5%. This may increase to 10% to 20% when a close family member has ADHD, around 30% when a sibling is affected, and nearly 50% when both parents have the condition. These estimates may vary between studies and populations. In clinical practice, parents may recognise that they experienced similar symptoms during childhood after their child has been diagnosed with ADHD.
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Research has also found an association between prenatal exposure to tobacco smoke or alcohol and an increased likelihood of ADHD in children. However, ADHD usually results from a complex interaction of genetic, biological and environmental factors rather than any single cause.
Symptoms of ADHD
It is common for school-age children to occasionally be inattentive, impulsive or overly active. These behaviours do not necessarily mean that a child has ADHD.
For an ADHD diagnosis, a child must display a sufficient number of characteristic symptoms in two or more settings, such as at home and at school. The symptoms must have been present before the age of 12, persisted for at least six months, and significantly affected the child’s social functioning, academic performance or behaviour. A formal diagnosis should be made by a qualified healthcare professional.
ADHD: Three Core Symptom Groups
Hyperactivity
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Appears restless, is constantly on the move and has difficulty controlling their activity
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Has difficulty playing or taking part in leisure activities quietly
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Is constantly “on the go”, as if driven by a motor
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Talks excessively, even when it is inappropriate to do so
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Runs about or climbs in situations where it is inappropriate
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Frequently fidgets or squirms in their seat and has difficulty remaining still
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Often leaves their seat in the classroom or in other situations where remaining seated is expected
Impulsivity and Difficulty with Self-Control
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Frequently interrupts or intrudes on other people’s conversations or activities
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Blurts out answers before questions have been completed
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Has difficulty waiting their turn
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Has difficulty compromising or giving way to others and may frequently come into conflict with other children
Inattention
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Often fails to pay close attention to details
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Frequently makes careless mistakes
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May overlook questions on the back of an examination paper or have difficulty reading questions carefully
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Is easily distracted by their surroundings
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Has difficulty maintaining attention during learning, homework, daily activities or play
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Has difficulty organising tasks and planning schoolwork or daily activities
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Often has a messy room or desk and finds it difficult to keep things organised
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Frequently loses items needed for school or daily activities, such as a diary, pens, homework or an Octopus card
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Often appears not to listen when spoken to directly
ADHD Presentations
Every child with ADHD presents differently, and the same symptoms may vary in severity. Based on the predominant symptoms, ADHD can be classified into three presentations:
Combined Presentation
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Symptoms of both inattention and hyperactivity/impulsivity are present
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The most common presentation, accounting for approximately 50% to 60% of people with ADHD
Predominantly Inattentive Presentation
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Symptoms are mainly related to inattention
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Accounts for approximately 30% of people with ADHD and is more commonly identified in girls
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Often becomes more noticeable during primary school
Predominantly Hyperactive/Impulsive Presentation
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Symptoms are mainly related to hyperactivity and impulsivity
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Accounts for approximately 10% of people with ADHD
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Symptoms may be noticed by teachers as early as kindergarten
Clinical data suggest that up to 75% of people with ADHD have at least one co-occurring mental health or developmental condition. The most common are oppositional behaviours, followed by emotional difficulties, sleep disorders and learning difficulties.
Approximately half of people with ADHD may also experience difficulties with motor coordination. This may be reflected in physical abilities such as balance and endurance, which can be less developed than those of other children of the same age.
ADHD Assessment and Diagnosis
During an ADHD assessment, the doctor will gather detailed information from several sources, including:
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The child’s behaviour in different settings, such as at home and at school
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The child’s academic performance, including homework and examination results, as well as their social functioning
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Questionnaires completed by parents and reports provided by the school
The doctor will consider all the available information together with observations made during the assessment before reaching a clinical diagnosis. In most cases, blood tests and brain scans are not required to diagnose ADHD.
ADHD Treatment
The main approaches to treating ADHD are medication and behavioural management.
Medication
In Hong Kong, medications commonly used to treat ADHD fall into two main categories:
Central Nervous System Stimulants
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Commonly used as a first-line medication for ADHD
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May help improve attention, reduce hyperactivity and strengthen self-control
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Work by regulating the activity of certain neurotransmitters in the brain
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Possible side effects include reduced appetite, sleep difficulties, gastrointestinal discomfort, abdominal pain, headaches and anxiety
Non-Stimulant Medications
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May help reduce inattention, hyperactivity and impulsivity
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May be more suitable for patients who:
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Do not respond adequately to stimulant medication
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Experience significant side effects from stimulants
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Have co-occurring conditions, such as anxiety
Behavioural Management
Improving Attention
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Minimise distractions in the surrounding environment
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Break tasks down into smaller steps that take approximately 20 minutes each
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Allow appropriate breaks between tasks
Developing Organisational Skills
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Establish a clear daily routine and follow it consistently
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Use checklists as reminders of tasks to complete or items to bring
Setting Clear and Specific Behavioural Goals
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Use a behaviour chart to record positive behaviours
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Provide immediate praise and rewards when the child demonstrates the desired behaviour
Some children with ADHD continue to experience symptoms as they grow older. Although hyperactivity may gradually decrease with age, difficulties with attention and organisation can persist into adulthood.