Methylphenidate for attention-deficit/hyperactivity disorder: The longest debate

It is difficult to debate 4 professors and the Journal Editor, in what might be termed the ‘long debate’ or the ‘longest debate’, dating back to the 1930s (Bradley, 1937). For a start, it should be pointed out that there appears some bias in the authors adding of italics to the Cochrane review’s overall conclusion that methylphenidate ‘may’ improve attention-deficit/hyperactivity disorder (ADHD) symptomology. The authors draw attention to Multimodal Treatment Study of Children With ADHD (MTA) findings that question the advantage of long-term medication. While not approaching the size and funding of the MTA, our 30-month follow-up of hyperactive children, was still clinically useful (Levy and Hobbes, 1982). This divided a clinical sample of children referred with possible hyperactivity into children who were not treated with medication, children who were still on medication and those who came off medication within the 30 months. The latter group was predicted by verbal/performance or performance/verbal discrepancies on psychometric testing while those still on medication had a median IQ of 85, compared with 100 in those coming off medication. It suggested that a subgroup of children treated for ADHD may have learning/developmental problems that no longer required medication with maturation and/or remediation. It also indicated that children referred for possible ADHD are not a homogeneous group and require individualised approaches. Thus, a small clinically based study indicated as far back as 1982, that at least a subgroup of ADHD children can come off medication within 30 months.

For an in-depth discussion of the long-term implications of the MTA study, I recommend a webinar of a talk given by James Swanson (one of the main MTA investigators) at the Karolinska Institute, that is reproduced in the chapter on Attention Deficit Disorder in the e-book ‘IACAPAP e-Textbook of Child and Adolescent Mental Health’, edited by Rey (2012). While Swanson points out that by 36 months the strong differences between medication treatment alone and behaviour therapy had washed out, he concedes that after the 14 weeks of intensive treatment had ceased, there was no capacity to monitor who went on to medication or not in the other groups, so the results relate to ‘intention to treat groups’ that could have reverted to various community-based treatments. He also concedes that while all the investigated groups levelled out in terms of symptom counts, their symptom levels were all still higher than those of an additional group of class-mates of the MTA cohort, added later to the study. Swanson additionally has found that while the amount of stimulant prescription rates for children in the United States appear to have levelled out or are levelling out, the great increase is in the adolescent and adult age group, and he speculates that this might relate to competitive pressures in the United States around college entry and performance.

The main thrust of Mulder et al. (2016) appears to be a concern about inappropriate long-term use of stimulants and possible unspecified side effects, in addition to demonstrated effects on growth. The authors neglect to say that these are dose related and clinically more likely at the time of the pubertal growth spurt. In relation to cognitive effects, Levy et al. (2013) demonstrated that the minor allele of the D1 dopamine receptor predicted ‘zombie-like’ cognitive/motor side effects in a subgroup of ADHD children. This finding should be replicated and implications followed up, but an National Health and Medical Research Council (NHMRC) application received good reviews, but no funding. While child psychopharmacological research is not supported in Australia/New Zealand, it is not surprising that parents continue to seek the support of the few child psychiatrists and increasingly more behavioural paediatricians who prescribe medication. There are many important heuristic questions raised by the use of stimulant medications that are worthy of more than Debate.