June 4, 2024
ADHD often includes a problem called disinhibition. This means that the brain struggles to control attention, thoughts, emotions, and behavior, which can lead to negative outcomes. Normally, inhibition helps people stay focused and avoid distractions, but when it fails, it's called disinhibition.
Children with ADHD who have problems with inhibition may face issues like substance abuse, self-harm, and antisocial behavior. Improving their inhibition can help them better manage themselves, do well in school, and have better relationships.
A team of researchers from China and South Korea explored whether physical activity could improve inhibition in children with ADHD. They reviewed studies and excluded those without control groups, those with poor quality assessments, and those involving other interventions like cognitive training or supplements. Their final analysis included 11 studies with 713 participants.
Key Findings on Physical Activity
Conclusion
The research concluded that physical activity can significantly improve the inhibition in children with ADHD, especially with regular, moderate-to-vigorous, open-skilled exercise done at least twice a week for an hour or more. Future studies should continue to explore this with high-quality methods to confirm these findings.
Meng Wang, Xinyue Yang, Jing Yu, Jian Zhu, Hyun-Duck Kim, and Angelita Cruz, “Effects of Physical Activity on Inhibitory Function in Children with Attention Deficit Hyperactivity Disorder: A Systematic Review and Meta-Analysis,” International Journal of Environmental Research and Public Health (2023) 20, 1032, https://doi.org/10.3390/ijerph20021032.
A team of Spanish researchers has published a systematic review of 16 studies with a total of 728 participants exploring the effects of physical exercise on children and adolescents with ADHD. Fourteen studies were judged to be of high quality, and two of medium quality.
Seven studies looked at the acute effects of exercise on eight to twelve-year-old youths with ADHD. Acute means that the effects were measured immediately after periods of exercise lasting up to 30 minutes. Five studies used treadmills and two used stationary bicycles, for periods of five to 30 minutes. Three studies "showed a significant increase in the speed of reaction and precision of response after an intervention of 20-30 min, but at moderate intensity (50-75%)." Another study, however, found no improvement in mathematical problem-solving after 25 minutes using a stationary bicycle at low (40-50%) or moderate intensity (65-75%). The three others found improvements in executive functioning, planning, and organization in children after 20- to 30-minute exercise sessions.
Nine studies examined longer-term effects, following regular exercise over many weeks. One reported that twenty consecutive weekly yoga sessions improved attention. Another found that moderate to vigorous physical activity (MVPA) led to improved behavior beginning in the third week, and improved motor, emotional and attentional control, by the end of five weeks. A third study reported that eight weeks of starting the school day with 30 minutes of physical activity led to improvement in Connor's ADHD scores, oppositional scores, and response inhibition. Another study found that twelve weeks of aerobic activity led to declines in bad mood and inattention. Yet another reported that thrice-weekly 45-minute sessions of MVPA over ten weeks improved not only muscle strength and motor skills, but also attention, response inhibition, and information processing.
Two seventy-minute table tennis per week over twelve weeks improved executive functioning and planning, in addition to locomotor and object control skills.
Two studies found a significant increase in brain activity. One involved two hour-long sessions of rowing per week for eight weeks, the other three 90-minute land-based sessions per week for six weeks. Both studies measured higher activation of the right frontal and right temporal lobes in children, and lower theta/alpha ratios in male adolescents.
All 16 studies found positive effects on cognition. Five of the nine longer-term studies found positive effects on behavior. No study found any negative effects. The authors of the review concluded that physical activity "improves executive functions, increases attention, contributes to greater planning capacity and processing speed and working memory, improves the behavior of students with ADHD in the learning context, and consequently improves academic performance." Although the data are limited by a lack of appropriate controls, they suggest that, in addition to the well-known positive effects of physical activity, one may expect to see improvements in ADHD symptoms and associated features, especially for periods of sustained exercise.
Noting that "Growing evidence shows that moderate physical activity (PA) can improve psychological health through enhancement of neurotransmitter systems," and "PA may play a physiological role similar to stimulant medications by increasing dopamine and norepinephrine neurotransmitters, thereby alleviating the symptoms of ADHD," a Chinese team of researchers performed a comprehensive search of the peer-reviewed journal literature for studies exploring the effects of physical activity on ADHD symptoms.
They found nine before-after studies with a total of 232 participants, and fourteen two-group control studies with a total of 303 participants, that met the criteria for meta-analysis.
The meta-analysis of before-after studies found moderate reductions in inattention and moderate-to-strong reductions in hyperactivity/impulsivity. It also reported moderate reductions in emotional problems and small-to-moderate reductions in behavioral problems.
The effect was even stronger among unmediated participants. There was a very strong reduction in inattention and a strong reduction in hyperactivity/impulsivity.
The meta-analysis of two-group control studies found strong reductions in inattention, but no effect on hyperactivity/impulsivity. It also found no significant effect on emotional and behavioral problems.
There was no sign of publication bias in any of the meta-analyses.
The authors concluded, "Our results suggest that PA intervention could improve ADHD-related symptoms, especially inattention symptoms. However, due to a lot of confounders, such as age, gender, ADHD subtypes, the lack of rigorous double-blinded randomized-control studies, and the inconsistency of the PA program, our results still need to be interpreted with caution."
A Chinese study team has performed an updated meta-analysis of randomized clinical trials (RCTs) published through July 2022, looking specifically at the effects of chronic exercise on ADHD core symptoms and executive functions in children and adolescents.
The researchers defined chronic to mean exercise interventions lasting at least six weeks, with the longest clocking in at well over a year (72 weeks).
They only included RCTs with blinding of all assessors who measured the primary outcomes, to guard against any conscious or unconscious bias.
A total of 22 studies met criteria for inclusion in the series of meta-analyses they performed. The RCTs were widely distributed, with four from North America, three from Africa, three from Europe, eleven from Asia, and one from Oceania.
Three studies were rated as being at low risk of bias, the other 19 at moderate risk of bias.
Meta-analysis of eleven RCTs with a combined 514 participants reported a small-to-medium reduction in ADHD core symptoms. Between-study variation (heterogeneity) was moderate, and there was no indication of publication bias.
Breaking that down by age group, for children (eight RCTs, 357 children) the reduction in core symptoms was likewise small-to-medium, versus a medium effect size reduction among adolescents (three RCTs, 157 adolescents), with no heterogeneity.
When the control group received no treatment or was sedentary (8 RCTs, 422 participants), the effect size remained small-to-medium, whereas when the control group received education, it became large (two RCTs, 58 participants).
Improvements in executive functions were even more pronounced. Meta-analysis of 17 RCTs with a combined 795 participants yielded a medium-to-large effect size reduction in executive functions overall. Heterogeneity was moderate, with absolutely no sign of publication bias.
More specifically, there was a medium effect size improvement in working memory (10 RCTs, 290 participants), a medium-to-large effect size improvement in cognitive flexibility (8 RCTs, 206 participants), and a large effect size improvement in inhibition (12 RCTs, 299 participants).
Once again, adolescents benefited more than children. Whereas children showed medium effect size improvements in executive function (14 RCTs, 659 children), adolescents registered enormous improvements (3 RCTs, 136 adolescents).
One note of caution, though. Among RCTs rated low risk of bias, effect size improvements in both ADHD core symptoms (3 RCTs, 180 participants) and executive functions (2 RCTs, 86 participants) were small and did not reach statistical significance. That suggests a need for more and better RCTs to reach a more settled verdict.
For now, the authors concluded, “This meta-analysis suggests that CEIs [chronic exercise interventions] have small-to-moderate effects on overall core symptoms and executive functions in children and adolescents with ADHD.”
Background:
Noting that “the results of previous investigations into the therapeutic benefits of probiotics in the treatment of ADHD symptoms remain inconsistent,” a Taiwanese study team conducted a systematic search of the peer-reviewed medical literature to perform a meta-analysis.
The Study:
The team identified seven randomized controlled trials (RCTs) that met criteria for inclusion: focusing on children and adolescents under 18, with ADHD diagnoses, comparing probiotic interventions with placebo, and using standardized behavioral rating scales to assess ADHD symptoms.
Meta-analysis of these seven RCTs with a combined total of 342 participants found no significant improvement in ADHD symptoms. In fact, six of the seven RCTs clustered tightly around zero effect, while the seventh – a small sample (38) outlier – reported a very large effect size improvement.
Meta-analysis of the three RCTs with a combined 154 individuals that used probiotics with single strains of microorganisms showed absolutely no improvement in ADHD symptoms with no between-study variation (heterogeneity).
Meta-analysis of the four RCTs with a total of 188 participants that used multiple strains pointed to a medium – but statistically nonsignificant – effect size improvement, with high heterogeneity. Removing the previously mentioned outlier RCT collapsed the effect size to zero.
Two of the RCTs (with 72 total individuals), including the outlier, offered probiotics in conjunction with methylphenidate treatment. Meta-analysis of the other five RCTs with 270 persons that were structured around pure supplementation yielded absolutely no improvement in ADHD symptoms with no heterogeneity.
Meta-analyses of the four RCTs with a combined total of 238 participants that examined ADHD subtypes reported no effect on either inattention symptoms or hyperactivity/impulsivity symptoms.
Trivially, given the lack of efficacy, probiotic regimens were tolerated as well as placebo.
The Take-Away:
Ultimately, this meta-analysis found no evidence that probiotics improve ADHD symptoms in children and adolescents. Across seven randomized controlled trials, results consistently showed no significant benefit compared to a placebo. While probiotics were well-tolerated, they did not meaningfully impact inattention, hyperactivity, or impulsivity. These findings suggest that probiotics, whether single or multi-strain, are not an effective treatment for ADHD.
Background:
Noting that “Previous research has demonstrated that attention significantly influences various domains such as language, literacy, and mathematics, making it a crucial determinant of academic achievement,” an international study team performed a comprehensive search of the peer-reviewed medical literature for studies evaluating effects of physical activity on attention.
The Study:
The team’s meta-analysis of ten studies with a combined total of 474 participants found moderate reductions in attention problems following physical activity. They found no significant evidence of publication bias, but there was considerable variation in outcomes between studies (heterogeneity).
To tease out the reasons for this variability, the team looked at specific attributes of the physical activity regimens used in the studies.
The seven studies with 168 participants that involved mentally engaging physical activity reported large reductions in attention problems, whereas the three studies with 306 persons that used aerobic exercise found no reduction whatsoever. Heterogeneity in the former was reduced, in the latter all but disappearing.
Comparing studies with other interventions as control groups (6 studies, 393 participants) with those with no intervention as control (4 studies, 81 participants), the former reported only small improvements in attention problems, while the latter reported large improvements.
Duration of physical activity made little difference. The four studies with physical activity of an hour or more reported better outcomes than the six with less than an hour, but the difference was not significant.
Greater frequency did make a difference, but in a counterintuitive way. The seven studies with one or two physical activity interventions per week (162 participants) reported large reductions in attention problems, whereas the three studies with three or more interventions per week (312 participants) showed no improvement.
Conclusion:
The authors concluded, “Our study suggests that cognitively engaging exercise is more effective in improving attention problems in school-aged children with ADHD.” Moreover, “the benefits of improved attention in school-age children with ADHD are not necessarily positively correlated with higher frequency and longer duration of physical activity.” Also keep in mind that exercise, while important for all children, should not replace medical and psychological treatments for the disorder.
The National Health Interview Survey (NHIS) is conducted annually by the National Center for Health Statistics at the Centers for Disease Control and Prevention. The NHIS is done primarily through face-to-face computer-assisted interviews in the homes of respondents. But telephone interviews are substituted on request, or where travel distances make in-home visits impractical.
For each interviewed family, only one sample child is randomly selected by a computer program.
The total number of households with a child or adolescent aged 3-17 for the years 2018 through 2021 was 26,422.
Based on responses from family members, 9.5% of the children and adolescents randomly surveyed throughout the United States had ADHD.
This proportion varied significantly based on age, rising from 1.5% for ages 3-5 to 9.6% for ages 6-11 and to 13.4% for ages 12-17.
There was an almost two-to-one gap between the 12.4% prevalence among males and the 6.6% prevalence among females.
There was significant variation by race/ethnicity. While rates among non-Hispanic whites (11.1%) and non-Hispanic blacks (10.5%) did not differ significantly, these two groups differed significantly from Hispanics (7.2%) and Others (6.6%).
There were no significant variations in ADHD prevalence based on highest education level of family members.
But family income had a significant relationship with ADHD prevalence, especially at lower incomes. For family incomes under the poverty line, the prevalence was 12.7%. That dropped to 10.3% for family incomes above the poverty level but less than twice that level. For all others it dropped further to about 8.5%. Although that might seem like poverty causes ADHD, we cannot draw that conclusion. Other data indicate that adults with ADHD have lower incomes. That would lead to more ADHD in kids from lower income families.
There was also significant geographic variation in reported prevalence rates. It was highest in the South, at 11.3%, then the Midwest at 10%, the Northeast at 9.1%, with a jump down to 6.9% in the West.
Overall ADHD prevalence did not vary significantly by year over the four years covered by this study.
This study highlights a consistently high prevalence of developmental disabilities among U.S. children and adolescents, with notable increases in other developmental delays and co-occurring learning and intellectual disabilities from 2018 to 2021. While the overall prevalence remained stable, these findings emphasize the need for continued research into potential risk factors and targeted interventions to address developmental challenges in youth.
It is also important to note that this study assessed the prevalence of ADHD being diagnosed by healthcare professionals. Due to variations in healthcare accessibility across the country, the true prevalence of ADHD may differ still.
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