Study Finds That ADHD Stimulants Have Negligible Effect on Adult Height

Background:

One of the more persistent concerns among parents of children with ADHD is whether stimulant medications will stunt their child's growth. A large Israeli cohort study now offers some of the most rigorous reassurance to date, and its methodology sets it apart from earlier research. 

The question has long been complicated by a more fundamental uncertainty: do growth differences in children with ADHD stem from the condition itself, from stimulant treatment, or from factors present before any medication is ever prescribed? Without a clear answer, clinicians and families have faced a genuine dilemma when weighing the benefits of stimulant therapy against potential long-term physical costs. 

Most previous studies compounded this difficulty by comparing group-average heights, which ignores the crucial variable of genetic potential. A child who is short relative to the general population may simply have short parents. Failing to account for this introduces systematic bias and can make medications appear more harmful than they are. 

The Study:

The Israeli research team addressed this directly. Using health records from a nationwide provider, they assembled a retrospective cohort of children born between 1995 and 2003, following them through 2023. This amount of time was long enough for all participants to have reached adult stature (defined as 17 or older for females, 19 or older for males). Their sample included 5,671 children with untreated ADHD, 11,846 who received stimulant treatment, and 47,258 non-ADHD controls. Children who took stimulants for only one to two months, or who had chronic medical conditions requiring long-term medication, were excluded to avoid confounding the results. 

Crucially, adult height was evaluated not against population norms but against each individual's expected height, calculated from parental heights using the Tanner-Goldstein-Whitehouse method, a standard approach for estimating genetic height potential via mid-parental height. 

When the researchers compared adult heights across the three groups using analysis of variance (ANOVA), they did find statistically significant differences. But statistical significance, particularly in studies with tens of thousands of participants, does not automatically translate into clinical significance. The effect sizes were consistently very small, and the absolute differences were under one centimeter, which is a margin considered clinically negligible. 

Their conclusion is measured but clear: after accounting for genetic growth potential, neither an ADHD diagnosis nor stimulant treatment was associated with meaningful reductions in adult height. The findings, they argue, support prioritizing behavioral and functional outcomes when making treatment decisions, since the risk of clinically significant height loss appears to be minimal. 

The Take-Away:

For families navigating ADHD treatment, the practical implication is significant: concerns about permanent growth suppression, while understandable, should not be the primary driver of whether or how long a child receives stimulant therapy. 

Michal Gabbay, Uri Gabbay, and Doron Carmi, “The impact of ADHD and neurostimulant treatment on normalized height deviance after accounting for genetic height potential,” Pediatric Research (2026), published online, https://doi.org/10.1038/s41390-026-04929-1

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ADHD medication and risk of suicide

ADHD Medication and Risk of Suicide

A Chinese research team performed two types of meta-analyses to compare the risk of suicide for ADHD patients taking ADHD medication as opposed to those not taking medication.

The first type of meta-analysis combined six large population studies with a total of over 4.7 million participants. These were located on three continents - Europe, Asia, and North America - and more specifically Sweden, England, Taiwan, and the United States.

The risk of suicide among those taking medication was found to be about a quarter less than for unmediated individuals, though the results were barely significant at the 95 percent confidence level (p = 0.49, just a sliver below the p = 0.5 cutoff point). There were no significant differences between males and females, except that looking only at males or females reduced sample size and made results non-significant.

Differentiating between patients receiving stimulant and non-stimulant medications produced divergent outcomes. A meta-analysis of four population studies covering almost 900,000 individuals found stimulant medications to be associated with a 28 percent reduced risk of suicide. On the other hand, a meta-analysis of three studies with over 62,000 individuals found no significant difference in suicide risk for non-stimulant medications. The benefit, therefore, seems limited to stimulant medication.

The second type of meta-analysis combined three within-individual studies with over 3.9 million persons in the United States, China, and Sweden. The risk of suicide among those taking medication was found to be almost a third less than for unmediated individuals, though the results were again barely significant at the 95 percent confidence level (p =0.49, just a sliver below the p = 0.5 cutoff point). Once again, there were no significant differences between males and females, except that looking only at males or females reduced the sample size and made results non-significant.

Differentiating between patients receiving stimulant and non-stimulant medications once again produced divergent outcomes. Meta-analysis of the same three studies found a 25 percent reduced risk of suicide among those taking stimulant medications. But as in the population studies, a meta-analysis of two studies with over 3.9 million persons found no reduction in risk among those taking non-stimulant medications.

A further meta-analysis of two studies with 3.9 million persons found no reduction in suicide risk among persons taking ADHD medications for 90 days or less, "revealing the importance of duration and adherence to medication in all individuals prescribed stimulants for ADHD."

The authors concluded, "exposure to non-stimulants is not associated with a higher risk of suicide attempts. However, a lower risk of suicide attempts was observed for stimulant drugs. However, the results must be interpreted with caution due to the evidence of heterogeneity ..."

December 13, 2021

Unmedicated Adult ADHD Linked to Dementia in Population Study

Background:

Noting that “the association between adult ADHD and dementia risk remains a topic of interest because of inconsistent results,” an Israeli study team tracked 109,218 members of a nonprofit Israeli health maintenance organization born between 1933 and 1952 who entered the cohort on January 1, 2003, without an ADHD or dementia diagnosis and were followed up to February 28, 2020. 

Israeli law forbids nonprofit HMOs from turning anyone away based on demographic factors,  health conditions, or medication needs, thereby limiting sample selection bias.  

The estimated prevalence of dementia in this HMO, as diagnosed by geriatricians, neurologists, or psychiatrists, is 6.6%. This closely matches estimates in Western Europe (6.9%) and the United States (6.5%). 

Method:

The team considered, and adjusted for, numerous covariates: age, sex, socioeconomic status, smoking, depression, obesity, chronic obstructive pulmonary disease, hypertension, atrial fibrillation, heart failure, ischemic heart disease, cerebrovascular disease, diabetes, Parkinson’s disease, traumatic brain injury, migraine, mild cognitive impairment, psychostimulants. 

With these adjustments, individuals diagnosed with ADHD were almost three times as likely to be subsequently diagnosed with dementia as those without ADHD. Men with ADHD were two and a half times more likely to be diagnosed with dementia, whereas women with ADHD were over three times more likely, than non-ADHD peers. 

More concerning still, persons with ADHD were 5.5 times more likely to be subsequently diagnosed with early onset dementia, as opposed to 2.4 times more likely to be diagnosed with late onset dementia. 

On the other hand, the team found no significant difference in rates of dementia between individuals with ADHD who were being treated with stimulant medications and individuals without ADHD. Those with untreated ADHD had three times the rate of dementia. The team nevertheless cautioned, “Due to the underdiagnosis of dementia as well as bidirectional misdiagnosis, this association requires further study before causal inference is plausible.” 

Conclusions and Relevance:

This study reinforces existing evidence that adult ADHD is associated with an increased risk of dementia. Notably, the increased risk was not observed in individuals receiving psychostimulant medication, however the mechanism behind this association is not clear.

These findings underscore the importance of reliable ADHD assessment and management in adulthood. They also highlight the need for further study into the link between stimulant medications and the decreased risk of dementia.

 

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February 25, 2025

Meta-analysis Finds Quality of Life Improvements Associated with ADHD Medications

Quality of life (QoL) is defined as a person’s satisfaction with their life, measured across several dimensions including psychological, social, health, biological, and economic well-being. For adults, these are usually self-reported. QoL for children and adolescents is usually reported by parents.  

Medications for ADHD include stimulants (methylphenidate and amphetamines) and non-stimulants (e.g., atomoxetine, clonidine, guanfacine, viloxazine). As QoL is related to ADHD symptoms’ severity, management of ADHD via medication could improve not only core symptoms but also QoL in people with ADHD.  

Noting the absence of meta-analytic evidence on the effects of ADHD medications on QoL, an international research team conducted a systematic review and meta-analysis of parallel or cross-over randomized clinical trials (RCTs) to estimate the effects of ADHD medication on QoL. They also performed secondary analyses to see if these effects differed in children and adolescents versus adults, as well as by class of medications, and if they were moderated by length of treatment. 

Meta-analyses of four RCTs with a combined total of 950 participants with ADHD (45% adults) found a medium effect size improvement among those receiving amphetamines by comparison with those receiving placebo. There was no sign of publication bias, but there was wide variation (heterogeneity) in effect size estimated among the studies.  

Meta-analysis of four RCTs with a combined total of 1,094 participants with ADHD (57% adults) found a small-to-medium effect size improvement among those receiving methylphenidate by comparison with those receiving placebo. Again, there was no sign of publication bias, but wide variation in effect sizes among the studies. 

Due to lack of sufficient data, the team could not explore whether length of treatment affected the results, or if there were differences between children/adolescents and adults. 

Finally, a meta-analysis of eleven RCTs with a combined total of 3,344 participants with ADHD (63% adults) likewise found a small effect size improvement among those taking atomoxetine compared with those receiving placebo. Once again, there was no sign of publication bias, but wide variation in effect sizes among the studies. 

The team was able to establish that for atomoxetine treatment, length of intervention – the studies ranged from 6 to 24 weeks – had no significant moderating effect. Similarly, they found no significant differences in effect on children and adolescents versus adults.  

A single RCT evaluating modafinil treatment in adults found no improvements at any dose, whereas a single RCT testing non-stimulant guanfacine reported a medium effect size improvement in QoL.  Modafinil is not FDA approved for ADHD but is sometimes used as a last resort if other treatments fail.

The team concluded that the FDA approved medications for ADHD were significantly more efficacious than placebo in improving QoL in people with ADHD.  The improvements in Q0L were, however, smaller than what has been found for improvements is the symptoms of ADHD (inattention, hyperactivity, impulsivity).  More work is needed to detect differences by age and length of treatment. 

August 12, 2024

A New ADHD Medication That Works Differently in the Brain

The FDA has approved a new once-daily pill called centanafadine (trade name SIMTRIYO®). Approved for adults and kids aged 6 and older (weighing at least 44 lbs / 20 kg), centanafadine is a new category of ADHD treatment that aims to give fast results with fewer of the downsides of traditional stimulants.

What Makes This Drug Different?

To understand why centanafadine is unique among medications for ADHD, it helps to look at how ADHD brain chemistry works:

  1. Norepinephrine: Powers focus, alertness, and attention span.
  1. Dopamine: Drives motivation, reward system, and decision-making.
  1. Serotonin: Regulates mood, anxiety levels, and emotional stability.

Stimulants like Ritalin and Adderall work mainly in the dopamine system.  Nonstimulants like atomoxetine, viloxazine, clonidine and guanfacine work mainly on the norepinephrine system.  Centanafadine is the first drug in a new class called NDSRIs (Norepinephrine, Dopamine, and Serotonin Reuptake Inhibitors). We can describe its effects as follows:

  • Heavy boost to Norepinephrine: Delivers the strong focus and attention boost you need.
  • Moderate, smooth increase to Dopamine: Helps with motivation and brain executive function without triggering massive dopamine spikes that lead to addiction or heavy crashes.
  • Moderate boost to Serotonin: Helps smooth out mood swings and keeps anxiety under control.

What Did Clinical Trials Show?

The FDA approved centanafadine based on studies involving thousands of adults, teens, and children. Here are the key findings:

Centanafadine showed some improvement in ADHD symptoms within the very first week of taking it although a full effect takes about six weeks.

In adult trials, taking 200 mg or 400 mg daily led to significant improvements in real-world skills:

  • Time management and prioritizing tasks
  • Starting projects without procrastinating
  • Planning complex tasks and staying organized
  • Short-term working memory

In trials with children (ages 6–12) and teens (ages 13–17), centanafadine significantly reduced core ADHD symptoms like hyperactivity, impulsivity, and lack of focus compared to a placebo.

About 30% to 40% of adults with ADHD also suffer from anxiety. Traditional stimulants can make anxiety worse. In a trial specifically designed for adults dealing with both ADHD and anxiety, centanafadine effectively treated ADHD symptoms without firing up their anxiety, which might be due to its serotonin boost.

Does Centanafadine have Side Effects?

While Centanafadine was well-tolerated by most people in studies, like any prescription medication, it comes with important safety guidelines.

Prescribing Warnings:

  • Suicidal Thoughts in Children: In trials for kids aged 6 to 12, centanafadine was linked to a higher risk of suicidal thoughts and behaviors compared to a sugar pill.  Although rare, parents and doctors should look for changes in mood or behavior, especially when starting or changing doses.
  • Stimulant Classification: Because it acts on central nervous system pathways, especially dopamine, centanafadine is classified as a CNS stimulant so might lead to addiction. While it has a much lower abuse risk than stimulants like Ritalin or Adderall, doctors should still evaluate patients for any history of substance abuse before prescribing.

Common Side Effects:

  • Kids & Teens: Decreased appetite, stomach ache, nausea, rash, and headache.
  • Adults: Dry mouth, difficulty sleeping (insomnia), decreased appetite, nausea, and headaches.

Other Warnings:

  • Heart & Blood Pressure: It can cause small increases in heart rate and blood pressure, so doctors will check these regularly.
  • Drug Interactions: It cannot be taken with certain antidepressants (MAOIs) due to dangerous blood pressure risks.

The Bottom Line

Overall, centanafadine is a new step forward in how we treat ADHD. Because it acts differently in the brain than traditional treatments, patients who struggle with stimulant-related anxiety or side effects may find it useful to explore with their doctor.

Nitrogen Dioxide Linked to Higher ADHD Risk: Insights from a Massive South Korean Study

A landmark nationwide study from South Korea has uncovered a significant link between prenatal exposure to air pollution — specifically nitrogen dioxide (NO2) — and an increased risk of ADHD in children. 

While researchers have long suspected that air pollutants interfere with fetal brain development through inflammation and oxidative stress, this study is one of the largest and most comprehensive of its kind, following nearly 1.5 million births for up to 13 years. 

Why South Korea? 

South Korea provided a unique countrywide “laboratory” for this research due to two key infrastructure strengths: 

  • Universal Health Data: A national insurance database that tracks the health outcomes of the entire population. 
  • Granular Air Monitoring: A network of 642 monitoring stations that allowed researchers to precisely estimate what pollutants mothers were breathing based on their postal codes. 

Key Findings: The “Smoking Gun” of NO2 

While the study looked at several pollutants, nitrogen dioxide — a byproduct of fossil fuel combustion in cars and power plants — emerged as the primary concern. 

Pollutant 

Association with ADHD Risk 

Nitrogen Dioxide (NO2) 

Strongest Link: Every 1-ppb (part-per-billion) increase in exposure linked to a 22% rise in risk. 

Sulfur Dioxide (SO2) 

Minimal Link: Only a slight 4% increase per ppb. 

Ozone (O3) carbon monoxide (CO), & particulates 

No significant association was found. 

The scale of the NO2 risk is particularly striking. Over the typical range of exposure levels found in the study (an interquartile range of 13 ppb), the data suggest a threefold increase in ADHD risk for children in the highest-exposure groups compared to the lowest. 

Accounting for Other Factors 

To ensure the results weren’t skewed by other variables, the researchers controlled for a wide range of confounders including: 

  • Socioeconomic and employment status. 
  • Maternal age and baseline health. 
  • The child’s sex. 
  • The presence of 14 different medical conditions around childbirth. 

The authors emphasized the strong association between maternal nitrogen dioxide exposure and ADHD, while also noting the small but significant association with sulfur dioxide.  

The Take-Away: A New Frontier for Public Health 

Historically, air quality laws have been designed to protect our lungs and hearts. However, this study adds to a growing body of evidence suggesting that the brain is likewise vulnerable. 

In a commentary on the findings, expert George Ayoub argued that “neurodevelopment should be explicitly considered” when governments perform cost-benefit analyses on air quality regulation.  My view is a bit different.  The association is intriguing but the study does not establish cause and effect.  Many statistically significant environmental risk associations for neurodevelopmental disorders have disappeared after controlling for maternal risk for ADHD.  I hope this research team will do those analyses if feasible.

New Meta-analysis Finds Structured Executive Function Training Largely Ineffective

Executive functions (EFs) are the cognitive control systems that allow people to pursue goals, make decisions, and adapt to changing circumstances. Researchers generally break them into three overlapping capacities: working memory (holding and manipulating information in mind), inhibitory control (suppressing impulses and filtering out distractions), and cognitive flexibility (switching between tasks or mental frameworks). Strong EFs in childhood predict academic achievement, social competence, and long-term mental health; weaknesses in these areas that go unaddressed can persist into adulthood, undermining school performance, career prospects, and well-being. 

The Background:

Interest in training these skills has grown rapidly, but most research has been conducted in Western settings. China presents a distinctive context. Collectivist values make group-based programs culturally natural, and parental investment in academic outcomes is high. Both of these factors should, in theory, work in an intervention’s favor. At the same time, tightly scheduled school days (sessions typically capped at 30 minutes or less) constrain what is actually deliverable. A growing number of randomized controlled trials (RCTs) have tested EF interventions with Chinese children, but until now, no one has pulled that evidence together systematically. 

The Study:

A new network meta-analysis did exactly that. The researchers screened RCTs involving Chinese children aged 3–12, including both typically developing children and those showing subclinical signs of ADHD or autism spectrum disorder (ASD), for instance, siblings of children with an ASD diagnosis. Children who already carried a formal neurodevelopmental diagnosis were excluded. Fifty-two trials covering nearly 3,000 children met the inclusion criteria. Interventions fell into four categories: 

  • Computerized adaptive n-back training with metacognitive coaching (strategy instruction and self-monitoring): 14 trials, 486 children 
  • Stop-signal and rule-switching tasks targeting inhibitory control and cognitive flexibility, delivered face-to-face: 18 trials, 632 children 
  • Hybrid physical-cognitive training moderate-to-vigorous aerobic exercise combined with concurrent cognitive demands (e.g., brisk walking while counting backward) in 20–30-minute sessions: 10 trials, 298 children 
  • Computerized cognitive flexibility training (set-shifting, dual-task coordination), self-paced with progressive difficulty: 10 trials, 312 children 

The headline finding is that three of the four intervention types produced statistically significant improvements across all three EF domains. The exception was the hybrid physical-cognitive program, which did not reach significance for inhibitory control. Positive results across the board might sound encouraging until you look at the actual effect sizes. 

The Results:

The actual effects were negligible. Every significant result fell well below what methodologists define as a “small” effect (a standardized mean difference, or SMD, of 0.2). The largest effect size in the entire analysis was an SMD of 0.097  (less than half that threshold). The authors summarize the interventions’ effects as “modest,” but that is generous phrasing for numbers that, in practical terms, amount to very little. The analysis also showed signs of publication bias, meaning that studies with null or negative results may not have been published, potentially inflating even these modest figures. 

The Take-Away: 

It is important to note that these results don’t necessarily mean that this is the last word on EF training. The results apply specifically to Chinese children working within the time constraints of Chinese school schedules, and they exclude children with diagnosed ADHD, a population for whom cognitive interventions sometimes show larger effects. Generalizing beyond those boundaries is unwarranted. 

What the findings do suggest is that structured EF programs, as currently implemented in Chinese educational settings, are not delivering meaningful real-world benefits. Statistical significance, it is worth remembering, is not the same as practical significance, and the gap between the two is sharp here. 

July 17, 2026