Evidence review: Physical exercise helps boost attention, cognitive flexibility and inhibitory control in children and adolescents with ADHD

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 Findings:

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:

• Does ADHD treat­ment enable long-term aca­d­e­m­ic suc­cess? (Yes, espe­cial­ly when phar­ma­co­log­i­cal and non-phar­ma treat­ments are combined)
• Sur­vey of 2500 fam­i­lies finds what ADHD treat­ments seem to work/ not work as applied in the real world
• What are cog­ni­tive abil­i­ties and how to boost them?