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ADHD: current opinion on diagnosis and treatment

Nikos Myttas
BA MD MRCPsych
Consultant in Child and Adolescent Psychiatry
East London and The City Mental Health NHS Trust
St Leonard's Hospital
London

The diagnostic concept of attention deficit hyperactivity disorder (ADHD) as it is defined today has undergone several changes since the first description of its cardinal signs and symptoms in 1902 by the eminent British paediatrician George Still.(1) At a meeting of the Royal Society of Medicine he presented the cases of 43 children who were often aggressive, defiant, resistant to discipline, excessively emotional or passionate, showed little inhibitory control, had serious problems with sustained attention and could not learn from the consequences of their actions. He proposed that these symptoms were all related to each other and they all had a common underlying neurological deficit. He speculated that they either had a low frustration tolerance or a frank neuroanatomical abnormality where their intellect could not control their will.
These children today would probably meet diagnostic criteria for ADHD with associated oppositional defiant disorder and/or conduct disorder. Before him, the German physician and poet Heinrich Hoffman described in 1865 "fidgety Philip" who "won't sit still, wriggles, giggles, swings backwards and forwards and tilts up his chair ... growing rude and wild".(2)
 
Clinical considerations
Neuroimaging and genetic studies, although still at an early stage, suggest that ADHD is a neuropsychiatric disorder where genetic inheritance accounts for 80% of the cases; the remaining 20% are accounted for by environmental insults to the brain, before during and after birth. Some will have both forms at the same time. Indeed, between 10 and 35% of children with ADHD have a first-degree relative with past or present ADHD, and approximately 50% of parents with ADHD will have a child with this disorder.(3) The majority of parents of affected children remain undiagnosed and untreated.
ADHD is one of the most common psychiatric disorders of childhood, affecting as many as 10% of school-age children. It is a heterogeneous condition that occurs across a continuum of severity and in one or more settings. It is almost always associated with a host of other conditions, such as learning disabilities, oppositional defiant disorder, conduct disorder, autism, coordination disorder, depression, anxiety and substance abuse.
At present there are no laboratory tests to confirm the diagnosis, which is based exclusively on a lengthy clinical interview. The criteria for making the diagnosis are in the International Classification of Mental and Behavioural Disorders, 10(th) Edition (ICD-10), or in the Diagnostic and Statistical Manual of Mental Disorders, 4(th) Edition (DSM-IV). In both, the behaviours to be recognised are very much the same but the symptoms are weighed and combined into categories differently.
For a child to meet the diagnosis the core signs of inattentiveness, overactivity and impulsiveness must be present from an early age, usually (but not always) before seven, they must have persisted continuously for over six months, they must have caused significant impairment in the child's academic, social and psychological functioning, and they must not be better explained by another mental disorder (such as depression or anxiety).
The ICD-10 criteria are stricter in that they stipulate that all three problems of inattention, hyperactivity and impulsiveness must be present at the same time, they must occur in two or more settings, and there must not be any other associated conditions (such as depression). As a result, the prevalence of hyperkinetic disorder, which constitutes a severe subgroup of ADHD, is about 1.5%.(4)
The DSM-IV allows for subtypes: "predominantly inattentive", "predominantly hyperactive-impulsive" and "combined". The symptoms must be present in at least one setting (home or school), and it acknowledges the presence of comorbid conditions as a rule rather than as an exception.
Although no two children present with exactly the same range or severity of symptoms and bearing in mind that ADHD is a dimensional condition, some children will be more seriously affected than others. However, there are several similarities worth mentioning.
Parents will often say that they first noticed their child not sleeping for more than 20 minutes at a time, crying incessantly, being restless and difficult to soothe for no apparent reason before their first year. As soon as the child was able to walk they ran rather than walked, got into everything, had minor accidents as a result of their overactivity, had little sense of danger and high tolerance to pain, was aggressive and loud in playgroups, and was beginning to show defiance for rules and low tolerance to frustration. By the age of four, the child would already have become impaired.(5,6)
In primary school they would be described as distractible and distracting others, disruptive, unable to concentrate on and complete their work, talking a lot, fidgeting, tapping, touching, making noises, swinging on their chair, complaining of boredom, getting up and walking about in class, being restless, interrupting others, unable to wait their turn, daydreaming, losing or misplacing their things, appear as not listening, forgetting instructions, repeating the same mistakes, not learning from the consequences of their actions, and domineering their relationships with their peers.
Their teachers would describe them as "underachievers", "lazy", "not reaching their potential", "disorganised", "lacking in concentration", "unmotivated" and "not trying hard enough", among others.
By the time the child had reached secondary school their academic, social and psychological standing would be seriously jeopardised: their school performance would have deteriorated, they would lag behind in academic skills, they would not have learnt how to prioritise and organise their affairs, they would have fallen out with their peers and got into fights, and more likely than not they would not have any friends. Self-esteem would have plummeted, and the first signs of anxiety, defiance and conduct disorder might have well settled in.

ADHD in boys and girls
The diagnostic criteria used by both manuals are behavioural, and they are the ones traditionally used to make the diagnosis. In clinic samples the ratio of boys to girls is between 6:1 and 12:1, suggesting a much higher prevalence of this condition in boys. However, in community samples the ratio is much lower, closer to 3:1, suggesting that girls tend to be undiagnosed. This is because girls do not display the disruptive behaviour more typical of the boys, and as a result girls have half the rates of oppositional defiant disorder and conduct disorder. However, they are much more likely to have social problems, and compared with boys they have higher rates of distress, anxiety and depression, they are more vulnerable to stress, they have a poorer self-esteem and they feel much less in control.(7) As a consequence, the atypical presentation of girls (predominantly inattentive) may be a barrier to early recognition and treatment. Interestingly enough, by early to mid-adolescence they develop higher rates of disruptive behaviour disorders, become more prone to smoking, alcohol and substance abuse, and are at a higher risk of academic failure and teenage pregnancy.

Comorbid conditions
It is rare for a child to have "pure" ADHD, and the coexisting of other disabling conditions is the rule. Such conditions include specific learning disorders (reading, writing, spelling), language disorders, motor coordination disorder, anxiety disorder, oppositional defiant disorder, conduct disorder, Tourette syndrome, and obsessive-compulsive disorder, and they are also at a higher risk of developing nicotine, alcohol and substance abuse.(8) Conversely, many children with mental retardation, autism, Asperger syndrome and nonverbal learning disability often have associated ADHD.

Aetiology
A number of neuroanatomical and physiological studies, although not conclusive, are implicating a dysfunction of the frontal-subcortical system (responsible for self-regulation) and suggesting an atypical pattern of brain development evident from early childhood. The major findings of these studies include smaller cerebral volume, smaller frontal lobe volume, smaller basal ganglia, reduced cerebellar size, reduced global cerebral metabolism(9) and an excess of slow-wave (theta) activity consistent with decreased alertness and underarousal.(10)
Perhaps the most promising research is in the area of neurotransmitters: genes for the dopamine receptors 4 (DRD4 7-repeat allele) and 5 (DRD5 148bp allele) and the dopamine transporter (DAT1 10-repeat allele) have been shown to be associated with an increased reuptake of the dopamine neurotransmitter from the synaptic cleft.(11) However, many of these risk alleles increase the risk only slightly, suggesting that ADHD is a complex disorder influenced by the interaction of multiple aetiological factors, each of which has only a minor effect.
There are also a number of well-documented environmental factors that either predispose to or precipitate the manifestation of ADHD symptoms, such as low birth weight, prenatal exposure to benzodiazepines, alcohol, cannabis and cocaine, idiosyncratic reactions to food substances, exposure to toxic levels of lead, early deprivation and institutional rearing.

Diagnostic process
This should include a thorough and detailed neuropsychiatric evaluation that should consist of a clinical interview with the parents and separately with the child, detailed information from the school, psychometric assessment, observation of the child during the clinical examination, assessment of language functioning and physical examination. The child and the parents should be seen on more than one occasion, and if in doubt a school observation may be indicated. Rating scales completed by parents and teachers can be useful, but they are not diagnostic in themselves.

Treatment
The vast majority of ADHD children have more than one problem, and therefore a multimode approach should be available and each problem dealt with separately. Psychoeducation should be the starting point, and it should ideally involve not only the parents and the child but also the other family members and school staff. An assessment of parental resources and capacity should be made, and parenting techniques should be discussed in a structured and detailed manner. Behavioural interventions should be tried both at home and in school, and serious attention should be paid to the child's academic functioning, with recommendations for remedial teaching.
There is a substantial body of evidence to support the use of stimulant medication (methylphenidate in various forms and dexamphetamine) in moderate-to-severe cases, combined with behaviour treatment, as the first treatment strategy.(12) Other nonstimulant drugs with research evidence for their effectiveness include tricyclic antidepressants (desipramine, imipramine), norepinephrine reuptake inhibitors (atomoxetine), antihypertensives (clonidine) and bupropion.
From time to time many diets and food supplements are promoted without the benefit of clinical trials, and many of the claims are subsequently proven to be wrong. Claims that food colourings, preservatives, salicylates, sugar, citrus fruit, strawberries and so on were the main cause of hyperactivity have not been substantiated. There are, however, a small number of children whose hyperactive behaviour is exacerbated by certain foods, and an elimination diet may help a minority of them. Fish oils have been widely promoted of late, but as yet there is not enough evidence to recommend their use.

Support groups
Community support groups have an invaluable role to play in providing support for the affected individual and his family, disseminating information about the disorder, public campaigning for the wider recognition of ADHD, offering advocacy services, running parent and teenager workshops and linking up with other volunteer sectors.

Conclusion
ADHD is a severe and disabling neurobiological disorder that runs a lifelong course and has serious consequences for the life of the affected individual and those around them if it remains undiagnosed and untreated. The risks of not treating ADHD include academic, social and psychological failure, unemployment, broken relationships, psychiatric disorders, and nicotine, alcohol and substance abuse. About 75% of young sufferers will carry the disorder into adulthood to a varying degree and often with crippling consequences.(13)

References

  1. Still GF. Lancet 1902;1:1008-12, 1077-82, 1163-8.
  2. Hoffman H. Die Geschichte vom Zappel-Philipp. Der Struwwelpeter. Germany: Pestalozzi-Verlag; 1865.
  3. Faraone SV, Doyle AE. Child Adolesc Psychiatr Clin North Am 2001;10:299-316.
  4. Swanson JM, et al. Lancet 1998;351:9100, 429-33.
  5. Barkley RA, Biederman J. J Am Acad ChildAdolesc Psychiatry 1997;36:1204-10.
  6. DuPaul GJ, et al. J Am Acad Child Adolesc Psychiatry 2001;40:508-15.
  7. Gaub M, Carlson CL. J Am Acad Child Adolesc Psychiatry 1997;36:1036-45.
  8. Wilens TE, et al. J Nerv Mental Dis 1997;185:475-82.
  9. Castellanos FX, Lee PP, Sharp W, et al. JAMA 2002;288:1740-48.
  10. Chabot RJ, Serfontein G. Biol Psychiatry 1996;40:951-63.
  11. Faraone SV, et al. Am J Psychiatry 2001;158:1052-57.
  12. NICE. Technology Appraisal Guidance No 13. Guidance on the use of Methylphenidate (Ritalin, Equasym) for attention deficit hyperactivity disorder (ADHD) in childhood. October 2000.
  13. Barkley RA, et al. J Am Acad Child Adolesc Psychiatry 1990;29:546-57.