Use of stimulants for attention deficit hyperactivity disorder

Short abstract

Definitive diagnosis of attention deficit hyperactivity disorder is complex. David Coghill believes the condition is undertreated, but Harvey Markovitch argues that current uncertainties about diagnosis and treatment mean doctors should be cautious

The consequences of persistent, pervasive, and disabling hyperactivity, impulsivity, and inattentiveness on a child's development and functioning are serious. The presence of attention deficit hyperactivity disorder (ADHD) or hyperkinetic disorder predicts a wide range of negative outcomes. These include poor self esteem, academic achievement, occupational status, peer relationships, and family functioning and increased injury rates, disruptive and antisocial behaviour, substance misuse, and mood and anxiety disorders.¹ As treatment can restore healthy functioning to many of these children and young people, a reluctance to diagnose ADHD seems unreasonable and withholding effective treatments from those who have had the condition diagnosed is unjustifiable.

Opponents of the validity of ADHD as a diagnosis cite our incomplete understanding of its precise biological basis. Sensationalist journalism has often caught public, and at times professional, attention by delivering negative messages about the “dangers” of stimulants such as methylphenidate and the sharp increases in use over the past decade. It is important, however, to examine this information in context.

The brain is the most complex of biochemical machines. The many technical and ethical constraints on studying its development and functioning make it unsurprising that we have no definitive causal models for any of the complex developmental psychiatric disorders. Indeed, it is impressive that we know as much as we do about the biological underpinnings of ADHD. Considerable convergent, replicated evidence now supports the role of complex polygenic and environmental factors in causing alterations in neural architecture and functioning; these changes result in a range of neuropsychological performance deficits and ultimately the behavioural symptoms associated with ADHD.²

Risks and benefits of stimulants

Scientific study shows that stimulants exert a positive effect on the biological and cognitive processes that are thought to cause ADHD. They improve the inhibition of inappropriate responses and cognitive flexibility and memory functioning^{w1 w2} rather than “doping children up” or turning them into “zombies,” as is often suggested in the media. Depression and emotional blunting are in fact uncommon but important adverse events with psychostimulants and respond to withdrawal of treatment.

Figure 1.

Where's my stimulant?

Credit: ANNABELLA BLUESKY/SPL

Systematic reviews and meta-analyses of evidence from short term studies have all concluded that both methylphenidate and dexamfetamine are effective and safe.³ Evidence from longer term studies, although still sparse, is starting to appear and supports continuing effectiveness and safety over the medium to long term.^w3 Importantly, neither methylphenidate nor dexamfetamine, both of which have been used for more than 50 years to treat the symptoms of ADHD in millions of children, have been associated with serious adverse events when used as a monotherapy, through either the pharmacovigilance systems or in peer reviewed journals.

More long term studies of psychostimulants are required. Before further progress can be made, however, the ethical and practical difficulties of designing and conducting such studies, and their high costs, must be acknowledged and tackled by researchers and funding bodies. One important recent finding warns of the broader risks and costs to the individual, the family, and society associated with undertreatment of ADHD. Huss and Lehmkuhl found a 50% reduction in rates of substance misuse in patients treated with stimulants compared with untreated patients.⁴

When and how should stimulants be used?

Recent studies have shown drug treatment has appreciable advantages over behavioural approaches and questioned the added effectiveness of a combined approach over drugs alone.^{5 w4} Evidence based and consensually driven clinical guidelines support the use of psychoeducational, pharmacological, and behavioural treatments for ADHD.^6-10 All propose that stimulants should be considered as potential first treatment, particularly for patients with the most severe, pervasive, and disabling symptoms. This does not exclude behavioural treatments, which remain an appropriate alternative first step in less severe cases (followed by a trial of drugs if ineffective) and as an adjunct to drugs in severe cases and in the management of associated and comorbid problems.

All the guidelines emphasise the need for a detailed, accurate, and comprehensive assessment by well trained and experienced specialist practitioners before starting treatment. In the United States, however, most treatment is carried out within a primary care setting with only a few patients ever having contact with a specialist services.^w5 As a consequence large variations in practice occur, and although only one in eight children with ADHD are treated with stimulants, half of those being treated do not meet the criteria for ADHD.^w6

Attitudes and practice also vary widely across the United Kingdom. In Scotland, for example, prescription rates for stimulants vary sevenfold among health boards.^w7 Although variability in the quality of assessment results in some inappropriate prescription of stimulants, the main evidence is for under-recognition and undertreatment. The National Institute for Clinical Excellence, using a conservative approach to decision making on treatment, reported that in England and Wales only 30% of patients with hyperkinetic disorder, the most severe form of ADHD, were receiving stimulants.⁷ Evidence suggests a similar situation in the rest of the United Kingdom. Thus, the increases seen in the prescription of psychostimulants over recent years represent less of a worrying explosion than a move towards better recognition and treatment of a serious childhood disorder.—David Coghill