December 11, 2021

Nationwide cohort study: methylphenidate reduces traffic accidents in persons with ADHD

Taiwan has a single-payer healthcare system that covers virtually every inhabitant (99.5%). That makes it relatively easy to track healthcare issues using its comprehensive National Health Insurance Research Database.

This database maintains a subset, the Longitudinal Health Insurance Database (LHID), consisting of a million persons, with no significant differences in sex, age, or healthcare use from the parent database.

A Taiwanese research team used the LHID to identify 114,486 individuals diagnosed with ADHD from 1997 to 2013. It then compared their motor vehicle (including motorcycles, which are extremely common in Taiwan) crash patterns with 338,261 normally developing controls from the same database.

Adjusting for sex, age, and psychiatric comorbidities, persons with ADHD were about a fifth (19%)more likely to be in traffic crashes. Breaking it down further by sex, women with ADHD were no more likely to be in crashes, but men with ADHD were about a quarter (24%) more likely than their healthy counterparts.

Since the database also tracks pharmaceutical prescriptions, the team also looked into the effect of methylphenidate (MPH), the medication that is the first-line treatment for ADHD under Taiwanese guidelines, and the only approved stimulant. Atomoxetine, a non-stimulant, is used where MPH is either ineffective or not indicated for any other reason and is only used in 4% of all cases.

Of the 114,486 persons diagnosed with ADHD, 89,826 used MPH, and 24,660 did not.

Compared with persons with ADHD who were not on methylphenidate, those with ADHD who were on MPH for 180 days (roughly half a year) or less had 77% fewer accidents, and those on MPH for over 180 days had 93% fewer accidents. This strong dose-response relationship is suggestive of a causal relationship, with MPH perhaps reducing impulsive behavior, particularly among young men with ADHD.

The team also conducted within-person analyses, comparing times when persons with ADHD were taking MPH with periods when they were not. These showed no effect within 30 days of use, rising to a 65%reduction in crashes within 60 to 90 days of use, which was barely outside the 95% confidence interval (p = .07), very likely because of "the extremely low incidence of transport accidence (i.e. 0.6%)enlarged the confidence interval."

The authors concluded, "All registration medical claim data came from the nationally-representative sample of NHI, minimizing the selection and recall bias. By excluding transport accidents before ADHD diagnosis, we have precluded the reverse association between ADHD and road traffic accidents as much as possible. The advantage of the between-subjects comparison was that we were able to examine the MPH effect in different dose groups. However, confounding by indication cannot be eliminated. For example, those with a severe degree of ADHD symptoms, an exhibition of risky behaviors, or comorbid with other psychiatric illnesses were more likely to be prescribed medication. Hence, we also performed within-subject comparisons to adjust for time-invariant factors."

Transport safety thus offers another compelling reason to treat ADHD symptoms. Methylphenidate in particular seems to be especially effective in reducing traffic fatalities and injuries.

Yi-Chun Liu, Vincent Chin-Hung Chen, Yao-Hsu Yang, Yi-LungChe, and Michael Gossop, "Association of psychiatric comorbidities with the risk of transport accidents in ADHD and MPH," Epidemiology and PsychiatricSciences30 (2021), e14, 1-9,https://doi.org/10.1017/S2045796021000032.

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Swedish Nationwide Population Study: Newborn Seizures Double Risk of ADHD

The first few weeks of life are the time when babies are most vulnerable to seizures (known as neonatal seizures). This is partly because of events that can occur during birth, and partly because the newborn brain is naturally in a more excitable state than a mature brain, making it more prone to seizure activity. 

Seizures affect roughly 1 to 3 in every 1,000 full-term babies born, and the rate is considerably higher in premature babies, at around 11 to 14 per 1,000. In most cases, seizures at this age are triggered by a specific event or injury affecting the brain. In full-term newborns, the most common cause is a condition called hypoxic-ischemic encephalopathy (HIE), which occurs when the brain is deprived of adequate oxygen and blood flow around the time of birth. Other causes include genetic or metabolic conditions, stroke, bleeding in the brain, and structural abnormalities in how the brain developed. In very premature babies, bleeding into the fluid-filled spaces of the brain (known as intraventricular hemorrhage) is the leading culprit. 

Diagnosing seizures in newborns is tricky because many normal or abnormal movements and behaviors in this age group can look like seizures without actually being them. For this reason, monitoring the baby’s brain activity using an electroencephalogram (EEG) – a test that records electrical signals in the brain – is essential to confirm whether a seizure is truly occurring. 

Sweden’s single-payer health system provides universal coverage, with national registers linking healthcare and population data. Researchers tracked infants with EEG/aEEG-confirmed seizures born between 2009 and 2020 and compared them to controls without neonatal seizures. 

Altogether, 1062 infants with neonatal seizures were matched with 5310 controls. 

The team adjusted for birth, mode of delivery, sex, birth weight, and Apgar scores – quick, standardized assessments used to evaluate newborns’ health minutes after birth. 

With these adjustments, infants who had neonatal seizures were twice as likely to subsequently be diagnosed with ADHD and three times as likely to be subsequently diagnosed with autism spectrum disorder.  

The authors emphasized that because the study was observational, it cannot demonstrate a direct cause-and-effect relationship between neonatal seizures and outcomes. Factors like seizure frequency, genetics, and socioeconomic status are thought to significantly impact the prognosis of affected children, but these could not be included in this study due to data limitations. 

March 18, 2026

Meta-analysis Finds Small to Moderate Benefits of Single Exercise Sessions for Adult ADHD

Background: 

There are currently few long-term treatment options for adult ADHD. Psychostimulants can help reduce symptoms, but their benefits rely on availability, continued use, and are not easily tolerated by some. Cognitive-behavioral therapies have also proven to be helpful, but access is limited because they must be provided by trained specialists. These challenges highlight the need to explore alternative interventions that could provide cognitive and behavioral improvements with fewer side effects. 

Exercise has shown potential as a nonclinical intervention for ADHD. Previous research indicates that physical activity can increase cortical volume, enhance brain activation, and boost connectivity in cognitive regions, as well as raise dopamine and norepinephrine levels – effects similar to psychostimulants. Research in children and teens with ADHD has found that both regular exercise programs and even single workout sessions can improve executive functions (mental skills like planning and self-control) and reduce core ADHD symptoms. But whether exercise helps adults with ADHD has remained an open question. 

Study:

A Chinese sports medicine research team set out to answer this by reviewing all available peer-reviewed studies on exercise and adult ADHD. They found so few studies on regular exercise programs – only four total, and three of those were small pilot studies just testing whether the approach was feasible – that they couldn’t draw firm conclusions about long-term exercise interventions. 

However, they were able to analyze four moderate-to-high-quality studies involving 152 adults with ADHD that tested single exercise sessions. The combined results showed moderate improvements in inhibitory control (the ability to resist impulses and stay focused). Adults not taking medication showed large improvements.  

When they looked at four studies involving 170 adults, they found small but consistent improvements in core ADHD symptoms after single exercise sessions. There was little to no variation (heterogeneity) in individual study outcomes, and no sign of publication bias. 

Results:

The team concluded, “Overall, these findings offer preliminary evidence on the potential role of exercise as a helpful strategy in the management of adult ADHD,” but cautioned that more well-designed randomized controlled trials are needed to determine the efficacy of both acute and chronic exercise interventions for adult ADHD, with particular emphasis placed on determining the best “prescription” for exercise – what type, how intense, and how often. 

They also noted that most existing research has focused narrowly on attention and impulse control, while other important mental abilities like working memory and mental flexibility remain largely unexplored. 

Take-Away

The takeaway here is practical and accessible: you don't need a long-term fitness program to get a cognitive bump from exercise if you have ADHD. Even a single session appears to help — particularly with impulse control. While the research base is still thin and we don't yet know the ideal exercise "prescription," the risk-benefit calculation is hard to argue with. For adults with ADHD who can't access medication or therapy, or who simply want an additional tool, breaking a sweat may be worth building into the routine.

Meta-analysis Finds People with ADHD Twice as Likely to Self-harm

Background: 

Non-suicidal self-injury (NSSI) means intentionally hurting yourself without trying to end your life. Common examples include cutting, scratching, or burning yourself. This behavior is most common in teenagers, affecting 13-20% of adolescents. It’s also called self-harm or deliberate self-injury. 

Young people who struggle with managing emotions, act impulsively, or have mental health conditions like depression are more likely to self-harm. 

Because ADHD involves impulsivity and often occurs alongside emotional difficulties, researchers have suspected a link between ADHD and self-injury. However, previous studies have tended to be small, unrepresentative, and inconsistent, making it hard to draw clear conclusions. 

The Study: 

Researchers combined results from 14 different studies involving nearly 30,000 people to get a clearer picture. They looked at children, teenagers, and adults with ADHD from various settings—including hospitals, community programs, and general population studies. 

To be included, studies had to confirm ADHD diagnosis through professional evaluation or validated testing methods. 

Key findings 

  • About 1 in 4 people with ADHD (27%) have engaged in self-injury. This rate was similar for adults (25%) and teenagers (28%).
  • People with ADHD had more than twice the odds (2.25 times higher) of self-injury compared to people without ADHD 
  • Girls and women with ADHD were at highest risk—they had four times higher rates of self-injury than boys and men with ADHD 

Conclusion: 

The researchers concluded that roughly one in four people with ADHD have engaged in non-suicidal self-harm. The findings suggest that ADHD and self-harm share overlapping vulnerabilities. 

Overall, this meta-analysis strengthens evidence that people with ADHD face a significantly elevated risk of non-suicidal self-injury, likely reflecting overlapping challenges with impulsivity, emotional regulation, and co-occurring mental health conditions. Importantly, this does not mean self-harm is inevitable in ADHD. It does, however, highlight the need for early screening, supportive environments, and targeted mental-health care to help reduce risk and support healthier coping strategies.

March 5, 2026