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May 22, 2024
Noting that the degree of comorbidity (co-occurrence) between epilepsy and ADHD “has never been quantified based on a systematic review with meta-analysis,” a Chinese study team based at Wuhan university has just reported findings based on doing just that.
Their systematic search of the peer-reviewed medical literature yielded 17 studies examining the prevalence of epilepsy among persons with ADHD, and 49 studies measuring the prevalence of ADHD among persons with epilepsy.
According to the Apple dictionary app, epilepsy is “a neurological disorder marked by sudden recurrent episodes of sensory disturbance, loss of consciousness, or convulsions, associated with abnormal electrical activity in the brain.” Its lifetime prevalence in the general population is about 0.76%, or about one in every 130 persons.
Meta-analysis of 17 studies with a combined total of over 900,000 participants spread over twelve countries on five continents yielded an epilepsy prevalence estimate of 3.4% among individuals with ADHD, or well over four times the prevalence in the general population. There was no sign of publication bias, but variability (heterogeneity) among studies was extremely high.
The worldwide prevalence of ADHD in children, on the other hand, is about 7.2%, affecting roughly one in fourteen.
Meta-analysis of 49 studies with a combined total of 172,206 persons from 16 countries on five continents reported an ADHD prevalence of just over 22% among persons with epilepsy. However, heterogeneity among studies was extremely high, and there was very strong evidence of publication bias.
Using the trim-and-fill correction for publication bias yielded a reduced estimate of 16%, which is still over twice the prevalence in the general population.
Furthermore, the authors noted, “Given that the large sample studies in this study are basically population-based studies and the small sample studies are hospital-based studies, there is also the possibility of Berkson’s bias. Specifically, patients with comorbidities are more likely to need help or seek medical advice. This possibility would yield a higher comorbidity rate in hospital-based studies.”
And that is exactly what emerged from subgroup analysis. The prevalence of ADHD in epilepsy among the hospital-based studies was 27.1%, over twice the 13.2% prevalence reported from the 13 population-based studies. The largest population-based study, a U.S. study with over 114,000 participants, yielded a prevalence of only 3.5%.
The authors cautioned that the very high degree of heterogeneity between studies indicates “it is inappropriate to consider the summary effect as representative of the real effect.”
Shun, Wang & Yao, Baozhen & Haiju, Zhang & Xia, Liping & Yu, Shiqian & Peng, Xia & Xiang, Dan & Liu, Zhongchun. (2023). Comorbidity of epilepsy and attention-deficit/hyperactivity disorder: a systematic review and meta-analysis. Journal of Neurology. 270. 1-13. 10.1007/s00415-023-11794-z.
The Background:
Motor vehicle crashes remain one of the most significant public health challenges in the United States. In 2022 alone, nearly 44,000 people died on American roads, and more than 2.6 million crash-related injuries required emergency care. Most people are familiar with the usual suspects: drunk driving, speeding, and distracted driving from phones. These risks are well-documented and the focus of ongoing public safety campaigns.
But a serious risk factor has been flying under the radar: untreated ADHD. Despite receiving little attention from the public, policymakers, or transportation safety agencies, it may belong in the same conversation as these better-known dangers.
ADHD is not currently recognized by the National Highway Traffic Safety Administration as a driving risk factor; yet inattention and impulsivity, two of its defining features, are consistently cited as common contributors to crashes. Beyond these core symptoms, adults with ADHD may also experience emotional dysregulation, which can further impair driving behavior.
The Research:
Prior studies on ADHD and crash risk have produced estimates ranging from a 5% to a 70% increase. This massive heterogeneity has made it difficult to draw firm conclusions. This new meta-analysis set out to offer some clarity on these numbers.
Researchers focused specifically on adults aged 18 to 65 with a formal ADHD diagnosis who were not receiving treatment, comparing them to controls without ADHD. Four studies met these criteria, collectively covering more than 2.75 million people.
The Results:
The findings were striking: untreated ADHD was associated with a 93% increase in crash risk (95% confidence interval: 88%–99%). There was no evidence of publication bias. Although there was meaningful variation across studies, most of it stemmed from the smallest study (just 36 participants) which reported an outlier estimate of a 16-fold increase.
To put the 93% figure in context: a separate meta-analysis found that alcohol use is associated with a 150% increase in crash risk. Another way to understand just how significant this risk really is, untreated ADHD raises crash risk by more than half as much as alcohol does.
The analysis also found a dose-response relationship between ADHD symptom severity and crash risk: each incremental increase in symptom severity corresponded to a 5–6% higher crash risk. At the highest severity levels, crash risk approached that associated with alcohol use. This gradient reinforces that we're not looking at a binary distinction between “has ADHD” and “doesn’t” — the worse the symptoms, the greater the danger on the road.
The Takeaway:
These findings have practical implications for patients, families, clinicians, and policymakers alike. Untreated ADHD is not a minor footnote in the driving safety literature; rather, it is a substantial, measurable, and potentially modifiable risk factor. The question of whether and how it should be factored into licensing policy, clinical practice, and public health messaging deserves serious attention.
As populations grow, more children are growing up surrounded by traffic noise and polluted air. In most cities, these two factors tend to go hand-in-hand; yet, most previous research has examined these exposures separately. Many reviews focused on a single pollutant (such as fine particulate matter, PM2.5), or on a single developmental window, such as pregnancy or early childhood. Few have asked how noise and air pollution compare as risk factors, or how prenatal and postnatal exposures differ in their effects.
A new meta-analysis set out to address those gaps. It examined evidence on both environmental noise and several major air pollutants in relation to ADHD, compared exposures before versus after birth, and pooled data across countries and regions. Eligible studies involved children and adolescents under 18, used objective measures of environmental exposure, and assessed ADHD using either clinical diagnosis or standardized rating scales.
Noise
Nine studies, combining data from over 100,000 children and adolescents (all in European countries and Canada) found that high noise exposure was associated with 3% greater odds of ADHD. Prenatal noise exposure showed no effect; childhood exposure alone drove the association, at 4% greater odds. This is a negligible effect size that could easily reflect unmeasured confounding factors rather than a true causal relationship.
Nitrogen dioxide
Thirteen studies covering nearly one million children and adolescents in Europe, Canada, China, and South Korea found that nitrogen dioxide (NO₂) exposure was associated with 11% greater odds of ADHD. As with noise, prenatal exposure showed no independent effect. When the analysis was restricted to the five studies that used clinical diagnoses alone — generally considered the most reliable measure — the estimated odds rose to between 20% and 80% higher. The wide range reflects substantial variation across studies.
Pollutants with no significant effect
Four studies (97,500 participants) examining nitric oxide (NO), three studies (over 63,000 participants) on ozone, and three studies (over 28,000 participants) on sulfur dioxide found no significant associations with ADHD.
Particulate matter
The strongest associations emerged for particulate matter. Twelve studies involving nearly 160,000 participants in China, the US, Canada, and Europe found that exposure to fine particles (PM2.5, 2.5 microns in diameter) was associated with 30% greater odds of ADHD. Ten studies covering more than a quarter of a million participants in India, China, South Korea, and Europe found that coarser particles (PM10, 10 microns) were associated with 50% greater odds. In both cases, prenatal exposure showed no association, which is consistent with the fact that fetuses do not breathe air through developed lungs. When restricted to clinically diagnosed ADHD, PM2.5 was associated with roughly 50% greater odds, and PM10 with more than double the odds.
The Results
Across all exposures examined, particulate matter showed the clearest and strongest associations with ADHD, followed by nitrogen dioxide. Noise reached statistical significance but at a trivially small effect size. Nitric oxide, ozone, and sulfur dioxide showed no significant associations.
The authors found no evidence of publication bias which strengthens confidence in the overall pattern. However, there was marked heterogeneity across individual studies: results varied considerably, which urges caution in treating any single estimate as definitive. These are associations, not proven causal relationships, and the possibility that unmeasured factors explain part of the signal cannot be ruled out.
The Background:
Over the past two decades, diagnostic rates for adult ADHD have roughly doubled, and stimulant prescriptions in the United States skyrocketed by more than 50% between 2012 and 2023, particularly among girls and women. While these medications help many individuals manage their symptoms, a landmark 2026 article published in European Neuropsychopharmacology tackles an important question that is rarely discussed: When should doctors and patients consider stopping them?
The Discussion:
To answer this, the American Society of Clinical Psychopharmacology (ASCP) gathered a task force of 45 international experts spanning 12 countries. Through a rigorous evaluation process, they reached an overwhelming agreement on a framework for "deprescribing", the planned, supervised reduction or cessation of a medication. Here are the core insights from these ground-breaking guidelines and what they mean for adults navigating long-term ADHD treatment.
When the Treatment Isn’t Yielding Benefits
One of the most straightforward reasons to consider stopping a stimulant is if it simply isn’t doing its job. The task force agreed that if a patient does not experience an optimal response, measured by actual symptom reduction, improved daily functioning, and a better quality of life, even after trying a high, optimized dose, it may be time to step back and look at alternative options.
Sometimes, the issue goes back to the initial evaluation. The criteria for diagnosing ADHD have expanded over the years, and brief psychiatric evaluations can occasionally lead to diagnostic inaccuracies. If a thorough reevaluation reveals that the original ADHD diagnosis was incorrect, the expert consensus is clear: stimulant deprescribing is appropriate unless another stimulant-responsive condition is evident. Furthermore, if a patient develops a persistent tolerance to the drug that cannot be resolved by safe dose adjustments, a temporary taper or drug holiday may be recommended.
When the Risks to Health Outweigh the Rewards
Our bodies and health needs naturally shift over time, meaning a medication that worked safely years ago might pose a threat to your health today. The experts concluded that deprescribing should be heavily considered if stimulants exacerbate a concurrent medical or psychiatric illness. For example, although rare, stimulants can unintentionally trigger mania or psychosis in adults with unstable or unrecognized comorbid bipolar disorder.
Physical health developments are equally critical. If an adult develops a newly arising or unstable cardiovascular condition, such as a cardiac arrhythmia, ischemia, or cardiomyopathy, the risk-benefit balance changes dramatically. Additionally, if severe side effects occur that cannot be managed by reducing the dosage, or if dangerous new drug-drug interactions emerge, stopping the medication under medical supervision protects the patient's long-term well-being.
Addressing Misuse and the Complex Role of Cannabis
Because stimulant medications target brain reward and wakefulness circuitry, they can foster a propensity for misuse. Studies indicate that more than 1 in 5 adults prescribed stimulants have misused them, and 1 in 6 have diverted their medication to others. The task force emphasizes that deprescribing is warranted if a patient persistently takes doses higher than prescribed against medical advice, uses the medication purely for unauthorized performance enhancement, or has an untreated, coexisting substance use disorder.
And what about cannabis? This topic sparked the most debate among the experts, falling just short of an official consensus with 71% agreement that regular cannabis use alone shouldn't automatically trigger a stimulant stoppage. Recognizing the complexity, such as how chronic cannabis use can overlap with ADHD executive function deficits, the task force proposed a structured monitoring approach instead of an immediate cutoff. Clinicians are encouraged to track the patient every 1 to 3 months using standardized symptom tools and random urine drug screens to verify whether cannabis use is actively neutralizing the stimulant's therapeutic benefits.
The Path Forward: Safe Tapering and Lifestyle Support
If you and your doctor decide that stopping a stimulant is the right path, it shouldn’t happen overnight. The task force strongly recommends that medications be gradually tapered off at a rate tailored to the individual to minimize potential disruptions and distinguish between transient withdrawal and a true return of ADHD symptoms.
Crucially, stopping a medication doesn't mean stopping treatment. The experts highlight that the success of any deprescribing plan is significantly enhanced when patients focus on optimizing modifiable lifestyle factors. Prioritizing sleep hygiene, staying physically active, and implementing structured behavioral strategies can support executive functioning and help sustain your cognitive gains even as the medication is reduced or eliminated.
The Takeaway:
The decision to continue or stop an ADHD medication is a deeply personal one that requires balancing real-world efficacy, safety, and individual health changes. These new consensus recommendations provide an essential roadmap to help adults navigate their long-term mental health journeys safely and effectively.
Are you or a loved one currently evaluating your long-term relationship with ADHD medication? Consider scheduling a check-in with your healthcare provider to discuss whether your current treatment plan still perfectly matches your health needs today.
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