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.”
A 2021 consensus statement by an international group of scientists and clinicians (Bauer et al.) recommended that pregnant individuals “forego [acetaminophen] unless its use is medically indicated,” due to the potential risk of developmental disorders such as autism and attention-deficit/hyperactivity disorder (ADHD).
A mostly Swedish research team, collaborating with a U.S. researcher, nevertheless noted that previous studies have been limited by:
Sweden has a single-payer health insurance system that includes virtually its entire population, and national registers that enable tracking the health history of mothers and their children, including their children’s siblings.
The team used the Swedish registers to identify the roughly two-and-a-half million children born in Sweden from mid-1995 through 2019. They were also able to identify all siblings to be able to control for otherwise unmeasured familial and genetic confounding.
Almost 186,000 of these children were exposed to acetaminophen during pregnancy.
After adjusting for available known confounders, including (but not limited to) child sex and birthdate, mother’s age and medical history, use of any other painkillers, use of any psychoactive medications, country of birth, residential region, smoking status, highest household education, and disposable income, children exposed to acetaminophen during pregnancy were 7% more likely to be diagnosed with ADHD subsequently than those who were not exposed.
However, roughly the same results were found for other painkillers, including aspirin, non-aspirin nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, and antimigraine medication. High doses of acetaminophen did not produce any stronger association with subsequent ADHD than low dosage.
Moreover, when confining results to siblings – 8,526 children who were exposed versus 87,679 who were unexposed – the association between acetaminophen use during pregnancy and subsequent offspring ADHD vanished altogether (and, again, at every dose level). The associations similarly vanished with every other painkiller medication.
The Swedish team concluded, “Acetaminophen use during pregnancy was not associated with children’s risk of autism, ADHD, or intellectual disability in sibling control analyses. This suggests that associations observed in models without sibling control may have been attributable to confounding.”
Antipsychotic medications are used to treat a variety of psychiatric disorders, including schizophrenia, bipolar disorder, sleeping problems, major depression, and severe anxiety.
Untreated maternal mental illness is associated with poor health outcomes for both mothers and their offspring. On the other hand, one must guard against any potential direct harms of medications on development – including neurological development – of the fetus.
Because prenatal use of antipsychotics is infrequent, previous observational studies have suffered from small sample sizes that have not enabled precise and reliable assessment of risk. The clinical decision about whether to continue antipsychotic treatment in patients who become pregnant has therefore remained inconclusive.
In search of more reliable guidance, an international study team conducted a systematic search of the peer-reviewed medical literature to perform the first meta-analysis on this topic.
They evaluated study quality and only included studies rated “good” or better.
Identification of ADHD was determined by clinical diagnosis.
Meta-analysis of four studies encompassing over eight million participants found a slight association. Children exposed to maternal antipsychotics during pregnancy were 11% more likely to be diagnosed with ADHD subsequently.
But even in observational studies with millions of participants, such associations – especially when slight to begin with – could be due to unmeasured confounders.
The team therefore compared children with gestational exposure to siblings from the same mother who were not exposed, to address shared genetic and social factors at the family level.
Meta-analysis of two population-based sibling-matched studies with a combined total of over 4.6 million participants in Denmark, Norway, Sweden, Finland, Iceland, and Hong Kong found no significant association between gestational exposure to antipsychotic medications and subsequent diagnosis of ADHD.
The team concluded, “Our systematic review and meta-analysis of observational studies indicates that the heightened risks of ADHD and ASD observed in children gestationally exposed to antipsychotics appear to be attributable to maternal characteristics, rather than having a causal relation to the antipsychotic itself.”
Most previous studies of suicide and self-harm risk among persons with ADHD have focused on adolescents and adults. They’ve also tended to be cross-sectional, analyzing data from a population at a specific point in time.
An Australian study team took a different approach, conducting a before-and-after study through the birth cohort of the Longitudinal Study of Australian Children (LSAC), comprising 5,107 children who have been followed up every two years since birth.
The diagnosis of ADHD was based on parents reporting that their child had received a diagnosis of ADHD at or before age ten.
Suicide and self-harm were defined as children’s self-report at age 14 of any thought or attempt of suicide and self-harm respectively over the past year.
The team adjusted for the following confounders: socioeconomic status, birth weight, ADHD medication history, maternal education level, maternal age at birth, experience in bullying victimization at age 12, and depression score based on Short Mood and Feelings Questionnaire (SMFQ).
Of the 5,107 participants, 3,696 had all the valid data required for analysis and were included in the final cohort. Of these, 3.6% were diagnosed with ADHD by age 10.
With a diagnosis of ADHD at age 10 and all other factors held constant:
Both depression and exposure to bullying were statistically significant mediators for the relationship. Nevertheless, depression and exposure to bullying each accounted for well under 10% of the overall effect.
Neither socioeconomic status nor maternal factors had any significant mediating effect on outcomes.
The authors concluded, “This study provides compelling evidence that children diagnosed with ADHD at the age of 10 years face significantly elevated risks of experiencing suicidal thoughts, planning, or attempts, as well as self-harm, by the age of 14 years, which underscores the critical importance of recognizing and addressing these heightened risks in children with ADHD.”
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