Attention-Deficit/Hyperactivity Disorer (ADHD)
Debate: Are stimulant medications for ADHD effective in the long-term?
Samuele Cortese, M.D., Ph.D, David Coghill, BSc, MB ChB, MD, James M. Swanson, PhD
Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most common diagnoses in child and adolescent mental health services, in the USA as well as in many other countries. Medication, including stimulant and non-stimulant options, is an important element of the multimodal approach to ADHD management. Stimulants are recommended as the first line pharmacological treatment.1 A recent study including data from over 150 million individuals in 13 countries showed an increase in the prevalence of ADHD medications use over the past 15 years in all countries, albeit with large variations across countries.2 One of the aspects that remains controversial in relation to stimulants pertains to their long-term effectives.
For this Debate article, we asked two experts in the field, Prof. James Swanson (University of California at Irvine) and Prof. David Coghill (University of Melbourne), to argue for “against” and “for”, respectively, in relation to the motion “Are stimulant medications for ADHD effective in the long-term”?
We hope that this debate will contribute to highlight the complexity of the issue and suggest possible ways to address it in a rigorous way form a methodological standpoint.
Against: James Swanson
Definition of terms is necessary to address the motion. First, “psychostimulants” are defined as methylphenidate and amphetamine, which inherently are short-acting drugs characterized by pharmacokinetic and pharmacodynamic properties of immediate-release formulations that act for a few hours. Sustained effects across the day can be achieved by controlled-release formulations, but carry-over to the next day is not significant, so on subsequent days these medications must be administered again to reinstate pharmacological effects. Second, “effective” refers to treatment-as-usual (not enhanced treatment, which refers to efficacious). Magnitude of effectiveness (e.g., small, medium or large effect size) for a given outcome depends on how treatment is delivered, which may differ by country, era, age, or other factors. Third, “long-term” refers to a given time frame (e.g., 1, 3, or 10 years), which can be specified as duration of treatment (for evaluating consistent use of medication) or as time since initiation of treatment (for evaluating history of medication use, including residual long-term effects after treatment stops). Given these definitions, the following questions address long-term effectiveness of stimulant medication.
Is there evidence from the gold standard (randomized clinical trials) for effectiveness for 1 year?
Modern meta-analyses of randomized clinical trials (RCTs) have not answered this question definitively, due to a lack of studies of long-term treatment, but the reviews cite sparse data to address it. Storebø et al.3 identified 185 trials that qualified for a Cochrane review, but only one was for long-term treatment in children, the Multimodal Treatment Study of ADHD (MTA). Cortese et al.4 identified 133 trials that qualified for a network meta-analysis review, but only one was for long-term treatment in adults, the Comparison of Methylphenidate and Psychotherapy in Adult ADHD Study (COMPAS), and none in children or adolescents (the MTA was excluded by its co-intervention design). In both reviews, estimates of average effect size for short-term treatment was large (for symptom-severity as an outcome), but for long-term treatment effect size diminished to 0.46 (medium) in the 14-month MTA efficacy trial of treatment-by-protocol 5 and to 0.27 (small) in a 12-month COMPAS effectiveness trial of treatment-as-usual.6
Sparse data from RCT studies suggest long-term effectiveness of long-term treatment-as-usual diminishes over time and is small for continuing treatment when long-term is specified as 1 year.
Is there evidence from observational cohort studies for significant effects for several years?
In typical studies, effectiveness has been estimated by comparing a stimulant-treated subgroup (typically around 75% of cases, including those that remain on medication and those that do not) to a stimulant-untreated subgroup. In two prominent studies, initial effectiveness dissipated over years in studies covering different eras and reporting different outcomes. For treatment-as-usual in the 1980s history of medication use had a large effect on protection from substance use at 4 years but the effect dissipated completely by 10 years.7 For treatment-as-usual in the 1990s, effect of assigned or history of treatment with medication on symptom severity was large at 1 year but dissipated completely by 3 years,5 and did not provide protection from substance use at 8 years.8
These long-term observational follow-up studies indicate a history of treatment with stimulant medication is not associated with long-term effectiveness for long time periods (3 to 10 years).
Is there evidence from analyses of national registries for long-term effects?
Analysis of national registries provide information about treatment-as-usual for a given country and era. For example, in Sweden from 2006-2009 the average treatment duration was about 2 years for stimulant medication in cases 16 years of age or older, and 58% of cases switched treatment status over the 4 years, generating an average 3 periods of treatment and non-treatment.9 An innovative within-individual comparison of outcome in these cross-over periods indicated criminality rate was lower by 30% during periods of treatment (the test for the short-term on-off effect). But, they also reported medication use in 2006 did not significantly lower the rate of criminality 3 years later in 2009 (the test for long-term effect).
This registry study suggests treatment-as-usual is inconsistent but is effective when medication is used compared to when it is stopped, but it is not effective in the long-term (specified as 3 years).
Is there evidence from cases with consistent long-term treatment for long-term effectiveness?
The reviews suggest the MTA is one of the few studies that can address this question. In the RCT phase, consistent treatment with stimulants for 14 months documented short-term efficacy (greater reduction in symptom severity than for behavioral treatment), but with an increase of average daily dose by about 20%. In the long-term naturalistic follow-up phase, consistent self-selected treatment (a decreasing percentage of cases over time, but with continued increases in daily dose) did not show relative effectiveness (defined as better outcome than the untreated subgroup, which also improved). Also, there was a reverse treatment-selection bias: subgroups with longer treatment (up to 10 years) had demographic advantages (i.e., higher family income and parental education) compared to untreated cases.5
When use of medication was continued for a decade, long-term effectiveness was not significant compared to when medication was never used or was stopped (which occurred in most cases).
Why do ADHD patients stop a treatment that has large short-term benefits?
It may be informative to consider speculative hypotheses about why most cases stop medication. In adult interviews in the MTA follow-up, the most frequent reasons given for stopping was "medicine not needed/helping”, which was endorsed by over 80% of the cases.10 One possibility (the “adherence hypothesis”) is that ADHD patients inappropriately stop treatment, but if they had continued long-term effectiveness would have occurred (suggesting education to change attitude or opinion). However, when medication was used consistently for 10 years in the MTA, outcome was not significantly better.5 Another possibility (the “tolerance hypothesis”) is that ADHD patients appropriately stop treatment because the initial large effects truly dissipate (suggesting changes in treatment-as-usual). Dissipation may be due to insufficient continued increases in daily dose in the long-term follow-up (as the approved maximum is approached) to overcome long-term tolerance hypothesized to accumulate with extended consistent treatment. A positron emission tomography (PET) study of long-term treatment with methylphenidate for 1 year showed that density of dopamine transporters in ventral striatal brain regions increased by 24%, suggesting a possible neural mechanism underlying long-term tolerance.11
Current guidelines may undermine long-term effectiveness. In long-term treatment, daily doses beyond the approved maximum may be required to maintain effectiveness, but in most clinical practices, this is not acceptable. Also, consistent treatment is recommended, but stopping and restarting may release tolerance and offer a more effective method of long-term treatment.
Conclusion about the motion: Are stimulant medications effective in the long-term?
Based on evidence from (1) RCT, observational, and registry studies; (2) patterns of medication use in clinical practice; (3) reasons given for stopping; and (4) pharmacological and neural adaptations to stimulant drugs, the motion should be defeated. The literature clearly documents short-term effectiveness (that certainly justifies clinical treatment), but critical studies also indicates effectiveness diminishes over time and in the long-term (defined as > 3 years) the average residual or continuing effects of treatment-as-usual are no longer clinically significant.
For: David Coghill
There is no simple answer to this question. It is however clear that the long-term effectiveness of ADHD medications, as currently used in routine clinical practice, is not as good as we would expected based on our knowledge of their short-term efficacy. I will however argue that this is a consequence of the way they are currently used rather than an inherent property of the medications themselves. My current clinical mantra that ‘ADHD is easy to treat, but hard to treat well’ reminds us that it is not enough just to write the prescription we need to ensure we give the right treatment, in the right dose and formulation, to the right person at the right time and to do this we need to work hard to assess outcomes.
Long-term effectiveness studies for ADHD medications are complicated to design well and no single study design will capture the entire picture. Although randomised controlled trials are the highest level of evidence most authorities agree that, when you have treatments as efficacious as the ADHD medications (methylphenidate and amphetamine derivatives and prodrugs, atomoxetine, guanfacine and clonidine) it is neither practical nor ethical to conduct long-term placebo controlled RCTs. As a consequence almost all of the RCT evidence for ADHD medications relates to short term studies. Whilst these provide strong evidence for short term efficacy4 they don’t speak to long-term effectiveness. The European Medicines Agency (EMA) recognizing that need additional evidence before licensing medications that will usually require to be taken for several years. They therefore introduced a requirement for companies to demonstrate longer term efficacy. This has generally been done through the use of randomised withdrawal designs that are designed to demonstrate continued efficacy over a period of 6-12 months. Several of these have been completed and published all of which, as expected, demonstrate continued efficacy.12 The EMA also insisted that all new ADHD medications demonstrate continued effectiveness, and assess adverse effects and safety up to 2 years. Again the studies completed so far support continued effectiveness, and, whilst highlighting the presence of common, expected adverse effects, have not identified any new safety signals or unexpected problems in targeted areas like growth and cognition.13
Recently another type of data have started to appear in the literature. These focus on real world outcomes distal to the clinical consultation. The best know examples are from Scandinavian registry studies and include reduction in criminality9 and improved educational outcomes.14 Other studies using powerful single subject case control designs have demonstrated improved health outcomes such as a reduction in trauma related ER visits.15 Whilst these are very important data which tell us a lot about the potential benefits of these medications they also have their limitations. A valid criticism of many of these studies is that they do not to take duration of treatment into account and it is therefore not possible to be certain whether these are truly long-term outcomes.
Whilst these findings are encouraging, they are not sufficient to argue conclusively for long-term effectiveness. The real word issues challenges to this assumption been highlighted through several carefully conducted longitudinal studies that draw a very different picture. They suggest that, whilst we can demonstrate positive short outcomes these are not sustained into the longer term. The standout example is the Multimodal Treatment study of Children with ADHD (the MTA).5 Over a 14 month RCT the MTA demonstrated that when carefully titrated and closely monitored, ADHD medications resulted in a strong clinical response that was superior to the treatment as usual comparison (which often involved medication). Once the researchers stepped back and the study became observational with all participants free to choose their own community treatment, the benefits seen for the ‘medication’ group dissipated and, whilst outcomes remained considerably improved compared to baseline, there were no differences between the previously randomised groups. At the final follow-up, 12-16 years after the start of the study, there were no observable differences in symptom ratings between those who had received negligible, inconsistent or consistent ADHD medication in the intervening years. Notwithstanding several methodological problems (e.g. clinical outcomes were measured between 12 and 16 years post randomization whilst medication use was only measured up to 10 years), taken as a whole the MTA findings do suggest that, as used in routine clinical care, ADHD medications do not result in more positive symptom outcomes compared with other clinical approaches. Does this mean that ADHD medications are not effective in long-term care? It might, and those who do not support the use of medication to treat ADHD are quick to jump to this conclusion. I suspect however that these data are telling us not that the medications don’t work but that we are not using them effectively. When the first results from the MTA were published I looked at them and asked myself ‘why do we not get these outcomes in our clinic? What are they doing that we aren’t?” After looking at the protocols the answer seemed to be: careful titrations, that may result in using higher doses than before and the high quality clinical monitoring with continuing review of progress and treatment adjustments that were based on the outcome measures. This of course made complete sense as it replicates the approaches we all know benefit those with other chronic disorders like diabetes. Adapted the MTA approach for our clinic and saw immediate clinically meaningful improvements in outcomes. Most importantly these improved outcomes were maintained over several years. Average outcomes (mean follow-up 4.5 years (1-10 years)), were as strong as those reported for the MTA and similar to those we had seen in clinical trials.16 We increased the proportion of responders from 44% to 67%, almost identical to the MTA 14 month outcomes.16 Clearly pragmatic implementation trials of these enhanced approaches into clinical care that demonstrate transferability and scalability are required. However I believe that these data provide strong initial evidence that, when used carefully, ADHD medications are effective in the long term.
References
1. National Institute for Health and Care Excellence (NICE). Attention deficit hyperactivity disorder: diagnosis and management. NICE Guideline [NG87]. Available at: . (Last acces on 17.0.19)
2. Raman SR, Man KKC, Bahmanyar S et al. Trends in attention-deficit hyperactivity disorder medication use: a retrospective observational study using population-based databases. Lancet Psychiatry 2018;5(10):824-835.
3. Storebo OJ, Ramstad E, Krogh HB et al. Methylphenidate for children and adolescents with attention deficit hyperactivity disorder (ADHD). Cochrane Database Syst Rev 2015;11:CD009885.
4. Cortese S, Adamo N, Del GC et al. Comparative efficacy and tolerability of medications for attention-deficit hyperactivity disorder in children, adolescents, and adults: a systematic review and network meta-analysis. Lancet Psychiatry 2018;5(9):727-738.
5. Swanson JM et al,. Long-term outcomes in the multimodal treatment study of ADHD (the MTA): From beginning to end, 2018, In Oxford Textbook for ADHD. Banachewski T, Coghill D, and Zuddas A, Eds.
6. Philipsen A, Jans T, Graf E et al. Effects of Group Psychotherapy, Individual Counseling, Methylphenidate, and Placebo in the Treatment of Adult Attention-Deficit/Hyperactivity Disorder: A Randomized Clinical Trial. JAMA Psychiatry 2015;72(12):1199-1210.
7. Biederman J, Monuteaux MC, Spencer T, Wilens TE, Macpherson HA, Faraone SV. Stimulant therapy and risk for subsequent substance use disorders in male adults with ADHD: a naturalistic controlled 10-year follow-up study. Am J Psychiatry 2008;165(5):597-603.
8. Molina BS, Hinshaw SP, Eugene AL et al. Adolescent substance use in the multimodal treatment study of attention-deficit/hyperactivity disorder (ADHD) (MTA) as a function of childhood ADHD, random assignment to childhood treatments, and subsequent medication. J Am Acad Child Adolesc Psychiatry 2013;52(3):250-263.
9. Lichtenstein P, Halldner L, Zetterqvist J et al. Medication for attention deficit-hyperactivity disorder and criminality. N Engl J Med 2012;367(21):2006-2014.
10. Brinkman WB, Simon JO, Epstein JN. Reasons Why Children and Adolescents With Attention-Deficit/Hyperactivity Disorder Stop and Restart Taking Medicine. Acad Pediatr 2018;18(3):273-280.
11. Wang GJ, Volkow ND, Wigal T et al. Long-term stimulant treatment affects brain dopamine transporter level in patients with attention deficit hyperactive disorder. PLoS One 2013;8(5):e63023.
12. Coghill DR, Banaschewski T, Lecendreux M et al. Maintenance of efficacy of lisdexamfetamine dimesylate in children and adolescents with attention-deficit/hyperactivity disorder: randomized-withdrawal study design. J Am Acad Child Adolesc Psychiatry 2014;53(6):647-657.
13. Coghill DR, Banaschewski T, Bliss C, Robertson B, Zuddas A. Cognitive Function of Children and Adolescents with Attention-Deficit/Hyperactivity Disorder in a 2-Year Open-Label Study of Lisdexamfetamine Dimesylate. CNS Drugs 2018;32(1):85-95.
14. Lu Y, Sjolander A, Cederlof M et al. Association Between Medication Use and Performance on Higher Education Entrance Tests in Individuals With Attention-Deficit/Hyperactivity Disorder. JAMA Psychiatry 2017;74(8):815-822.
15. Man KK, Chan EW, Coghill D et al. Methylphenidate and the risk of trauma. Pediatrics 2015;135(1):40-48.
16. Coghill D, Seth S. Effective management of attention-deficit/hyperactivity disorder (ADHD) through structured re-assessment: the Dundee ADHD Clinical Care Pathway. Child Adolesc Psychiatry Ment Health 2015;9:52.
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