Produced by the Royal College of Physicians of Edinburgh and Royal College of Physicians and Surgeons of Glasgow

Attention Deficit Hyperactivity Disorder (ADHD)

  • Dr F Forbes, Consultant Child and Adolescent Psychiatrist, Child and Family Mental Health Service, Royal Hospital for Sick Children, Edinburgh, Scotland


Attention Deficit Hyperactivity Disorder (ADHD) is one of the most misunderstood medical conditions. Despite a plethora of scientific evidence, it is still being regarded by some as a diagnostic excuse for appalling childhood behaviour due to inadequate or inappropriate parenting. In this article Dr Fiona Forbes, an expert in child and adolescent psychiatry, provides an overview to aid the diagnosis and treatment of this much misperceived condition. (Image - ©

Key Points

  • Attention Deficit Hyperactivity Disorder (ADHD) is a common, chronic neurodevelopmental disorder; it is estimated it affects 5% of children and is up to four times more common in boys than in girls. Attention Deficit Hyperactivity Disorder is not medicalised ‘bad behaviour’ or ‘bad parenting’.
  • It is a risk factor for a wide range of adverse sequelae, including conduct disorder, academic and occupational underachievement, and poor peer and family relationships.
  • There is an increased rate of associated disorders including learning difficulties, developmental coordination disorder, anxiety and mood disorders.
  • Multimodal assessment and intervention is indicated.
  • Treatment should include education of child, family and school about ADHD; behavioural strategies at home and at school, and in most cases, medication.
  • The more recent development of a non-stimulant drug, atomoxetine, licensed to treat ADHD, has afforded greater choice for parents and clinicians, although most UK specialists would use this as a second line drug.
  • Stimulant drugs, methylphenidate and dexamfetamine, are effective in treating core ADHD symptoms in at least two-thirds of correctly diagnosed children, and are relatively safe.

Declaration of interests: The author has previously received funding from two drug companies, both of which produce drugs to treat ADHD, to attend conferences. This funding is now lapsed (nil in last 2 years).

What is ADHD?

Children with Attention Deficit Hyperactivity Disorder (ADHD) have persistent and disabling levels of restlessness and impulsiveness (‘hyperactive-impulsive’ sub-type) or inattention (‘inattentive’ sub-type) or all three (‘combined’ type), beyond developmental norms. Attention Deficit Hyperactivity Disorder is the term used in the American Diagnostic Classification System (the Diagnostic and Statistical Manual (DSM)) DSM-IV. The International Classification of Diseases (ICD) system, ICD-10, uses the term Hyperkinetic Disorder (HKD), and its diagnostic criteria are more strict; the core symptoms of HKD, impaired attention and overactivity, need to be be evident in more than one situation and onset must be before the age of six years. As with DSM-IV, symptoms need to be of at least six months’ duration. HKD equates best with the ‘combined’ type of ADHD. However, the term ‘ADHD’ has become common parlance, even among UK specialists.

It is a common, chronic neurodevelopmental disorder affecting many areas of a child’s life, with a high rate of secondary problems and a high rate of associated disorders. It requires multimodal assessment and management, usually including medication.

What is it not?

Attention Deficit Hyperactivity Disorder is not a ‘new’ disorder; nor is it medicalised ‘bad behaviour’ or medicalised ‘bad parenting’.

Descriptions of attention disorders can be found as far back as 1798, when Crichton, a physician, described two types of ‘morbid attentional disorders’, one of which would be consistent with the DSM-IV inattentive subtype.1

How common is it?

The prevalence rates of the broader category of ADHD vary considerably across studies where there are often major methodological differences; most would concur that a conservative estimate would be 5%.

The point prevalence of the more severe form of ADHD, HKD, is about 1.5% in the primary school age population. In the UK, the rates from epidemiological studies published in the 1980s and 1990s, remained around 1.5%; however the rate of recognition of the disorder rose dramatically during this same period in UK. It is up to 4 times more common in boys than in girls.

What causes it?

The cause of ADHD is unknown, but it is likely that there are several different causal pathways linking risk factors to the behavioural symptoms of ADHD. There is a hereditary component, and various environmental and genetic risk factors have been identified. Environmental risk factors include antenatal exposure to toxins (alcohol, benzodiazepines, nicotine), obstetric complications, brain disease and injury, and severe early deprivation. A recent meta-analysis of molecular genetic studies found a significant association between ADHD and dopamine system genes, especially DRD4 and DRD5.2 Converging research evidence, and the mode of action of drugs effective in treating ADHD, suggest dysregulation of brain catecholaminergic systems may play a role.

Why is it important?

Children with ADHD are at increased risk of a wide range of adverse sequelae, including low self-esteem, academic underachievement, poor peer relationships, disrupted family relationships, accidents and anti-social behaviour. They may also be at increased risk of later substance misuse.

ADHD is also associated with an increased rate of other disorders, including depression, anxiety, other behavioural disorders, tic disorders, specific learning difficulties and developmental co-ordination disorder. Sleep problems are common.

ADHD is a chronic disorder at least two-thirds of children continue to have ADHD symptoms through adolescence and, for some of them, symptoms persist into adulthood. Early diagnosis and intervention with the implementation of a long-term management plan is therefore crucial.


If the core features of ADHD are present (inattention; impulsiveness; over-activity), referral for specialist assessment is indicated, usually to the local child and adolescent mental health service (CAMHS) although in a few areas, community paediatricians have developed specialist interest in ADHD. The diagnosis of ADHD is a clinical one. There are no s