Overview
Attention deficit hyperactivity disorder (ADHD) describes persistent inattention and/or hyperactivity-impulsivity that interferes with functioning or development. For a diagnosis of ADHD to be valid, the following must be met:
- Starts before 12 years of age
- Present for ≥6 months
- Interferes with, or reduces the quality of social, academic, or occupational functioning
- Consistent across ≥2 settings (e.g. not just in school)
Epidemiology
- ADHD has 3 different subtypes based on the predominant feature:
- Combined subtype – up to 75% of cases
- Inattentive subtype – up to 30% of cases
- Hyperactive-impulse subtype – up to 15% of cases
- ADHD is more common in boys, however, this may be due to under-recognition in girls
- Most children are diagnosed at 3-7 years old
- There may be a genetic component to ADHD
Risk Factors
Overview
The exact cause of ADHD is unknown but it is thought to be due to altered brain neurochemistry and structure. Some risk factors include:
- Family history – there is a good amount of evidence suggesting a genetic component to ADHD
- Pregnancy:
- Low birth weight
- Alcohol smoking during pregnancy
- Maternal smoking
- Preterm delivery
- Maternal mental health disorders
- Other:
- Acquired brain injury
- Lead exposure
- Iron deficiency
Diagnosis
Definitions
Inattention describes difficulties in sustaining attention when required.
- In children, this may manifest as wandering off, lacking persistence, or being disorganised
Hyperactivity describes excess activity when it is not appropriate:
- In children, this may be excess motor activity (e.g. fidgeting) or running
- In adults, this may be extreme restlessness or wearing out others with their hyperactivity
Impulsivity describes rushed actions that occur in the moment without prior thought that have potential harm to the person. Examples are:
- Running to cross the road without looking
- Making important decisions without considering the long-term consequences (e.g. taking on a job without enough information)
- Social intrusiveness such as interrupting others excessively
Overview
The diagnosis of ADHD is made by a specialist in secondary care. Since many of the features of ADHD are common normally in childhood, features must demonstrate an adverse impact on the child. For a diagnosis of ADHD, the DSM-V criteria state that all of the following conditions are met:
- Starts before 12 years of age
- Present for ≥6 months
- Interferes with, or reduces the quality of social, academic, or occupational functioning
- Consistent across ≥2 settings (e.g. not just in school)
- The symptoms are not better explained by another mental disorder
- The threshold of certain features is met:
- For children, ≤16 years old, 6 of the features of ADHD below must be present
- For those aged 17 and older, 5 of the features of ADHD must be below and present
Features of ADHD
Features of inattention:
- Fails to pay close attention to details, makes careless mistakes in schoolwork, at work, or with other activities
- Has trouble holding attention on tasks/play activities
- Does not seem to listen when spoken to directly
- Does not follow through on instructions and fails to finish schoolwork/chores/duties at work (e.g. loses focus or gets sidetracked)
- Avoids/dislikes/reluctant to do work that requires sustained mental effort (e.g. schoolwork or homework)
- Loses things necessary for tasks and activities (e.g. pens, pencils, books, wallet, glasses etc.)
- Easily distracted
- Forgetful in daily activities
Features of hyperactivity and impulsivity:
- Fidgets/taps with hands or feet/squirms in seat
- Leaves seat when remaining seated is expected
- Runs about or climbs when it is not appropriate to or in older children, feeling restless
- Unable to play or take part in activities quietly
- Talks excessively
- Blurts out an answer before a question has been completed
- Has trouble waiting their turn
- Interrupts or intrudes on others (e.g. butting into a conversation)
Management
Overview
Assessing and managing ADHD is performed in secondary care and involves educating parents/carers and the child about ADHD, arranging strategies regarding behaviour management, and pharmacological therapy if watching and waiting does not work.
In general:
- 1st-line: watch and wait for 10 weeks and refer to a paediatrician if this is unsuccessful
- Drug therapy is a last resort if conservative management has failed. It is only available for those aged >5 years old:
- 1st-line: methylphenidate – monitor height, weight, and blood pressure
- Other options include lisdexamfetamine and atomoxetine
- If the child has a history of cardiovascular disease or features suggestive of heart disease (e.g. syncope, shortness of breath on exertion, chest pain etc.), refer to a cardiologist before starting medication for ADHD.
In general, ADHD medication is titrated in secondary care and may be monitored in primary care as part of a shared-care agreement.
Monitoring and Patient Advice
- Effectiveness, adverse effects of drugs, weight, height, blood pressure, and heart rate are measured at regular intervals
- Seek specialist advice if there are any derangements in these
- Do not routinely recommend cutting out certain foods (e.g. those with artificial colourings). If there is a link between symptoms and certain foods, refer the patient to a dietician who can help with dietary removal safely
Prognosis
- In general, over time, inattentiveness tends to persist and hyperactivity and impulsivity tend to receive
- Around 65% of patients are in ‘partial remission’ at 25 years old with some persistence of symptoms and continuing functional impairment
