Evidence and belief in ADHD

Attention deficit hyperactivity disorder (ADHD) generates controversy. Some believe that it does not exist, whereas others see the reluctance of clinicians to diagnose and treat it as denying effective health care to children.¹ Epidemiological studies show that 3-5% of children of school age may be classified as having attention deficit hyperactivity disorder.² No validated diagnostic test exists to confirm the clinical diagnosis.

It is a complex neurodevelopmental constellation of problems rather than a single disorder. The core symptoms are inattention, hyperactivity, and impulsivity. These are also, however, normal behavioural traits present in unaffected children. The extent to which each causes disability varies and should be seen within the context of a child's developmental level. For example, an active 3 year old, impulsive and frequently interrupting of others, differs from a disruptive, unfocused 8 year old who is unable to cope educationally. Yet both may display core symptoms. Also, it is important to establish that symptoms exist in various settings and are not better accounted for by another mental disorder.² Specialists should undertake this assessment.

The variability of treatment and concerns about overuse of stimulants has led to the writing of practice parameters,³ clinical guidelines, and evidence based briefings⁴ to support clinicians in achieving best practice. Prescriptions in the United Kingdom rose from 183 000 in 1991 to 1.58 million in 1995.⁵ The use of stimulants varies worldwide—it is estimated to be 10 to 30 times as high in North America as in the United Kingdom.⁶ Concern has been expressed about the rise in the use of psychoactive drugs, especially in preschool children in the United States.⁷

For parents and children, getting information about ADHD is a lottery that depends on which professional they see and what they read or gather from television and the internet.

What roles should the general practitioner, child psychiatrist, child psychologist, and paediatrician play? Szatmari suggests that our most important function is that of interpreting evidence.⁸ Through dialogue with parents and children the risks and benefits of treatment may be considered along with the family's values and cultural background. Transparency is essential, and requires that clinicians are able adequately to interpret less than perfect evidence.

Two new studies add to the debate. The collaborative multimodal treatment study of children with ADHD is the largest, most rigorous randomised controlled trial in ADHD research thus far.⁹ About 579 children aged 7 to 9.9 years with ADHD were assigned to four groups: medication management, intensive behavioural treatment, medication management plus intensive behavioural treatment, and standard community care. It showed significantly greater improvement among groups that were given medication. These results are in keeping with other studies examining drug treatment of ADHD with stimulants and confirm that these benefits continue during treatment.¹⁰ Serious methodological issues have been raised,¹¹ however, including that of the evaluation of non-drug interventions.⁶

The systematic review from McMaster University¹ reviews 77 randomised controlled trials, including the collaborative multimodal treatment study, and also incorporates results from the systematic review by researchers at the University of British Columbia.¹⁰ It concludes that stimulants are effective in the short term, are more effective than placebo, compare well with each other, and seem to be more effective than tricyclics and non-drug treatments.

The short term benefits of stimulants seem to continue into the longer term as long as they are taken, but evidence is limited in this area.⁹ Little is known, for example, about outcomes such as educational achievement, employment, or social functioning.¹ Adverse reactions are usually dose related and no evidence exists of harmful long term effects of therapeutic use.¹

Most importantly, the McMaster review highlights shortfalls in the published research. Many studies are small and do not adequately describe randomisation or blinding ,or account for withdrawals and dropouts.¹ Poor reporting of these basic methodological components limits our ability to assess the importance of published work, which is important to individual clinicians, systematic reviewers, and organisations (such as the National Institute of Clinical Excellence in England and Wales) that evaluate and summarise research. Many of the trials will have included these elements in their protocols and execution, yet they are absent from the final publication. Authors, peer reviewers, and editors should be encouraged to apply publication standards as recommended in the CONSORT (consolidation of the standards of reporting trials) statement.¹²

Stimulants should be prescribed judiciously and monitored carefully by specialists in close liaison with primary care physicians. Informed decision making by clinicians and parents will be aided by more attention to research methods and its improved reporting. The imminent report by the National Institute for Clinical Excellence on the use of methylphenidate in childhood hyperactivity will, we hope, assert this principle.