Rationale for psychostimulants in ADHD

Editor—Confusion about levels of diagnosis causes most debate about psychostimulants in childhood behavioural disorders.¹ DSM-IV definitions are all syndromes—that is, symptoms and signs unrelated to pathology and aetiology. Most effective therapies treat pathology and aetiology; syndromes can be treated only symptomatically. The syndrome of chronic diarrhoea is analogous. Gluten intolerance is one cause. If we suspect this clinically, we test the person by gluten challenge. Clinical improvement on withdrawal and relapse on challenge confirms the diagnosis. No clinical response excludes gluten intolerance. Most chronic diarrhoeas have other causes, and some persons with proved gluten intolerance have other clinical features.

Research has found defects in dopamine transport in the brains of children with clinical attention deficit hyperactivity disorder.²,³ Some children with the biochemical defect have other symptoms; some are clinically normal. Some with clinical attention deficit hyperactivity disorder are biochemically normal. Clinical and biochemical changes overlap but do not coincide. We can call the clinical condition “attention deficit hyperactivity syndrome” and the biochemical disorder “stimulant responsive behavioural disorder.” Symptoms in children with the biochemical disorder improve dramatically with psychostimulants.⁴ A formal, short term trial is needed. We should give long term psychostimulants only when the symptoms are severe but not necessarily typical of attention deficit hyperactivity syndrome, improve on psychostimulants, and return when they are stopped.

Stimulant responsive behavioural disorder is a group of defects of dopamine transport in the brain, with varying clinical expressions, including the attention deficit hyperactivity syndrome, but that syndrome also has other causes. Separating the biochemical disorder and clinical syndrome promotes the rational use of psychostimulant drugs.