The impact of physical exercise on ADHD has been examined in a large number of studies. Collectively, these studies have examined whether exercise reduces on core ADHD symptoms, e.g., inattention and hyperactivity/impulsivity, and strengthens executive functions, e.g., inhibitory control, working memory, and mental health, e.g., emotional and social functioning. Overall, results across multiple studies suggest a positive impact of physical activity (PA) on several of these outcomes in youth with ADHD.
Conclusions based on a single study –no matter how strong the study design and execution may be– are necessarily limited, however. This has led researchers to combine results from multiple studies using a statistical technique called meta-analysis so that more robust and reliable estimates of a treatment’s impact can be determined.
Meta-analyses also have limitations, however. Decisions made about which studies to include vs. exclude, how to adjust for potential biases in individual studies, etc., can lead different meta-analyses of the same issue to reach somewhat different conclusions, even when the studies examined in each meta-analysis overlap substantially.
Umbrella reviews provide an even higher level of synthesis than meta-analysis by statistically combining the results across multiple meta-analyses. Systematic methods are used to grade the quality of individual meta-analyses and decisions about inclusion vs. exclusion are made based on that grading. Other techniques adjust for risk of bias in studies and other potentially confounding factors. Ultimately, this method is intended to provide an even more robust estimate of an intervention’s impact than can be obtained from a single meta-analysis.
The new study:
A study just published in a recent issue of e Clinical Medicine [The efficacy of physical exercise interventions on mental health, cognitive function, and ADHD symptoms in children and adolescents with ADHD: an umbrella review] presents results from this type of umbrella review on the issue of PA as an intervention for youth with ADHD.
The authors began by systematically searching for meta-analysis examining the impact of PA on core ADHD symptoms, executive functioning, and/or mental health outcomes on youth with ADHD. Both randomized controlled trials and non-randomized studies were included.
After excluding meta-analyses that did not conform to pre-determined criteria, 10 meta-analytic studies were selected for the umbrella review. Nine of the 10 studies were graded to be of high quality and one was grade medium quality. Over 100 different outcomes were estimated across these studies and provided the basis for the overarching analyses for the umbrella review.
The evidence was classified into one of five categories (convincing, highly suggestive, suggestive, weak, or not significant) for each of the different outcome domains, with the following results:
Core ADHD symptoms: Physical activity was found to have Highly Suggestive evidence for reducing symptoms of inattention. Evidence supporting benefits on hyperactivity/impulsivity was not significant.
Executive functioning: Physical activity was found to have Highly Suggestive evidence for increasing cognitive flexibility (i.e., the ability to adapt to new, changing, and unplanned events), and inhibitory control (i.e., the ability to control our automatic urges by pausing, then using attention and reasoning to respond appropriately). Evidence supporting benefits on working memory was weak.
Mental health: Weak support was found for the impact of PA on emotional functioning and social functioning.
After adjusting for studies with high risk of bias, and estimating impact based only on studies that employed randomized-controlled trials, results remained largely similar. Evidence supporting the impact of PA on working memory, however, increased from weak to to highly suggestive.
Does the type, intensity, or duration of PA matter? The authors intended to conduct more nuanced analyses to learn whether the type of PA, intensity of PA, and duration of PA mattered. However, the number of studies available to address these questions was not sufficient.
Summary and implications:
Results from this comprehensive umbrella review on the impact of physical activity on core symptoms, executive functions, and mental health in youth with ADHD finds high suggestive evidence for beneficial effects in several domains. Parents, educators, and clinicians can thus have greater confidence that efforts to engage youth with ADHD in regular physical activity is thus likely to provide at least some benefits.
The conclusions that can be drawn even from this comprehensive review are constrained, however, by limitations in the available data and studies. Especially noteworthy is that it was not possible to ascertain what type, intensity, and duration of PA is necessary to either obtain benefits or to maximize benefits. While these dimensions of PA may not matter, they may also matter a great deal, and having better info on this would clearly be helpful in terms of the clinical applications of this work.
In addressing other limitations within the existing research base, the authors noted that it was not always possible to determine whether assessors were blinded during data collection. This is a significant issue as non-blinded raters could contribute to enhancing the apparent benefits of PA on whatever outcomes were being considered. It’s equivalent to doing a medication trial when everyone knows who is getting the drug and who is receiving placebo.
And, they noted several important types of outcomes, e.g., quality of life, resilience, self-esteem, anxiety, depression, etc., have not been examined in studies of PA with ADHD youth. Thus, the range of outcomes researchers have so far considered is constrained. It is striking that although ADHD is the most extensively researched mental health condition in youth, highly important issues like this remain largely unaddressed. This highlights how challenging this work is to do, but also how important it remains for the field to continue moving forward.
– Dr. David Rabiner is a child clinical psychologist and Director of Undergraduate Studies in the Department of Psychology and Neuroscience at Duke University. He publishes the Attention Research Update, an online newsletter that helps parents, professionals, and educators keep up with the latest research on ADHD.
The Study in Context: