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October 10, 2025
Vitamins play important roles in metabolism, immune regulation, and neurodevelopment. Recent studies show that deficiencies in vitamins like D, B6, B12, and folate are common in people with ADHD and ASD (autism spectrum disorder), and are associated with behavioral, cognitive, and brain development issues.
The Study:
A study team based in China has just performed a systematic search of the peer-reviewed medical literature to perform meta-analyses of clinical trials exploring vitamin interventions in the treatment of ADHD and ASD.
ADHD trials included participants with an official diagnosis. The primary intervention was vitamin supplements, while other treatments, including medications, remained unchanged or were excluded during the study period. ADHD outcomes included measurable changes in ADHD symptoms using validated rating scales and executive function measures.
Eligible studies included standard or sham control groups, crossover, parallel, or other clinical trial designs. In crossover studies, only first-phase data were analyzed to prevent carryover effects.
Ten trials with 852 participants met the standards, but meta-analysis showed no significant results. The outcomes varied widely, suggesting a need to distinguish among vitamins.
Results:
Of the five trials involving 347 participants that specifically evaluated vitamin D supplementation, results indicated a large effect size improvement in ADHD symptoms and executive function measures. The other five studies did not show any observable improvement.
Key limitations include:
The team concluded, “This meta-analysis supports the use of vitamin supplementation as a promising adjunctive treatment for ASD and ADHD. Vitamin B showed greater benefits in improving symptoms of ASD, while vitamin D was more effective in managing ADHD-related behaviors. These findings suggest that specific vitamins may target disorder-specific symptoms. Despite limitations such as the lack of trials on other vitamins and limited understanding of underlying mechanisms, vitamin therapy remains a low-cost, accessible option.”
An important limitation of this work is that the positive results for vitamin D were due to two studies from Iran. So far, no positive study has emerged from a non-Iranian study.
Interpretation:
The vitamin D findings are intriguing and could be important if replicated outside of Iran. Since supplementation is already widely recommended to those with limited sunlight exposure, clinicians may want to consider monitoring their patients’ vitamin D intake, especially in the winter months. It should be noted, however, that due to the limitations of this study, the results are by no means conclusive, and vitamin D should not be taken as a stand-alone treatment for ADHD.
Yonghui Shen, Yangbing Xie, Yadan Zheng, Yanbin Zheng, and Yan Liu, “Vitamin Interventions in ASD and ADHD: Systematic Review and Meta-Analysis,” Neuropsychiatric Disease and Treatment (2025) 21:1845-1855, https://doi.org/10.2147/NDT.S553063.
The Background on ADHD and Vitamin D:
In a blog published in the early days of The ADHD Evidence Project, we discussed an Iranian study examining the association between Vitamin D levels and ADHD in children. The meta-analysis combined 13 studies for a total of 10,344 participants. The researchers found that youth with ADHD had "modest but significant" lower serum concentrations of 25-hydroxyvitamin D compared to those without ADHD.
They also identified four prospective studies that compared maternal vitamin D levels with the subsequent development of ADHD symptoms in their children. Two of these used maternal serum levels, and two used umbilical cord serum levels. Together, these studies found that low maternal vitamin D levels were associated with a 40% higher risk of ADHD in their children.
Ultimately, the researchers noted that this result "should be considered with caution" because it was heavily dependent on one of the prospective studies included in the analysis. We concluded our blog by pointing out that further research, including more longitudinal studies, is needed before clinicians should start recommending vitamin D supplementation to ADHD patients.
Further Research:
Since publishing that initial blog, several more studies have been published about this association.
The World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Disorders (CANMAT) convened an international task force involving 31 leading academics and clinicians from 15 countries between 2019 and 2021. Their goal was to provide a definitive, evidence-based report to assist clinicians in making decisions around the recommendation of nutraceuticals and phytoceuticals for major psychiatric disorders.
For ADHD, the guidelines found only weak support for micronutrients and vitamin D in treatment. Overall, the task force concluded that nutraceuticals and phytoceuticals currently offer very limited evidence‑based benefit for ADHD management.
Another study published in 2023 systematically assessed the results of previously published studies to examine the associations between maternal vitamin D levels, measured as circulating 25(OH)D levels in pregnancy or at birth, and later offspring psychiatric outcomes. This study found a clear association between maternal vitamin D deficiency and subsequent offspring ADHD. They concluded, “Future studies with larger sample sizes, longer follow-up periods, and prenatal vitamin D assessed at multiple time points are needed.” To that, I will add that studies of this issue should use genetically informed designs to avoid confounding.
Conclusion:
Taking into account the updated research on the topic, there does seem to be an association between low prenatal vitamin D levels and the risk of subsequent offspring ADHD, but it is too soon to say it is a causal relationship due to the possibility of confounding. There is no high-quality evidence, however, that supplementing with vitamin D will significantly reduce symptoms in current ADHD patients.
A large international research team has just released a detailed analysis of studies looking at the connection between parents' mental health conditions and their children's mental health, particularly focusing on ADHD (Attention Deficit Hyperactivity Disorder). This analysis, called a meta-analysis, involved carefully examining previous studies on the subject. By September 2022, they had found 211 studies, involving more than 23 million people, that could be combined for their analysis.
Most of the studies focused on mental disorders other than ADHD. However, when they specifically looked at ADHD, they found five studies with over 6.7 million participants. These studies showed that children of parents with ADHD were more than eight times as likely to have ADHD compared to children whose parents did not have ADHD. The likelihood of this result happening by chance was extremely low, meaning the connection between parental ADHD and child ADHD is strong.
The researchers wanted to figure out how common ADHD is among children of parents both with and without ADHD. To do this, they first analyzed 65 studies with about 2.9 million participants, focusing on children whose parents did not have ADHD. They found that around 3% of these children had ADHD.
Next, they analyzed five studies with over 44,000 cases where the parents did have ADHD. In this group, they found that 32% of the children also had ADHD, meaning about one in three. This is a significant difference—children of parents with ADHD are about ten times more likely to have the condition than children whose parents who do not have ADHD.
The researchers also wanted to see if other mental health issues in parents, besides ADHD, were linked to ADHD in their children. They analyzed four studies involving 1.5 million participants and found that if a parent had any mental health disorder (like anxiety, depression, or substance use issues), the child’s chances of having ADHD increased by 80%. However, this is far less than the 840% increase seen in children whose parents specifically had ADHD. In other words, ADHD is much more likely to be passed down in families compared to other mental disorders.
The study had a lot of strengths, mainly due to the large number of participants involved, which helps make the findings more reliable. However, there were also some limitations:
Despite these limitations, the research team concluded that their analysis provides strong evidence that children of parents with ADHD or other serious mental health disorders are at a higher risk of developing mental disorders themselves. While more research is needed to fill in the gaps, the findings suggest that it would be wise to carefully monitor the mental health of children whose parents have these conditions to provide support and early intervention if needed
If we are to read what we believe on the Internet, dieting can cure many of the ills faced by humans. Much of what is written is true. Changes in dieting can be good for heart disease, diabetes, high blood pressure, and kidney stones to name just a few examples. But what about ADHD? Food elimination diets have been extensively studied for their ability to treat ADHD. They are based on the very reasonable idea that allergies or toxic reactions to foods can have effects on the brain and could lead to ADHD symptoms.
Although the idea is reasonable, it is not such an easy task to figure out what foods might cause allergic reactions that could lead to ADHD symptoms. Some proponents of elimination diets have proposed eliminating a single food, others include multiple foods, and some go as far as to allow only a few foods to be eaten to avoid all potential allergies. Most readers will wonder if such restrictive diets, even if they did work, are feasible. That is certainly a concern for very restrictive diets.
Perhaps the most well-known ADHD diet is the Feingold diet(named after its creator). This diet eliminates artificial food colorings and preservatives that have become so common in the western diet. Some have claimed that the increasing use of colorings and preservatives explains why the prevalence of ADHD is greater in Western countries and has been increasing over time. But those people have it wrong. The prevalence of ADHD is similar around the world and has not been increasing over time. That has been well documented but details must wait for another blog.
The Feingold and other elimination diets have been studied by meta-analysis. This means that someone analyzed several well-controlled trials published by other people. Passing the test of meta-analysis is the strongest test of any treatment effect. When this test is applied to the best studies available, there is evidence that the exclusion of fool colorings helps reduce ADHD symptoms. But more restrictive diets are not effective. So removing artificial food colors seems like a good idea that will help reduce ADHD symptoms. But although such diets ‘work’, they do network very well. On a scale of one to 10where 10 is the best effect, drug therapy scores 9 to 10 but eliminating food colorings scores only 3 or 4. Some patients or parents of patients might want this diet change first in the hopes that it will work well for them. That is a possibility, but if that is your choice, you should not delay the more effective drug treatments for too long in the likely event that eliminating food colorings is not sufficient. You can learn more about elimination diets from Nigg, J. T., and K.Holton (2014). "Restriction and elimination diets in ADHD treatment."Child Adolesc Psychiatr Clin N Am 23(4): 937-953.
Keep in mind that the treatment guidelines from professional organizations point to ADHD drugs as the first-line treatment for ADHD. The only exception is for preschool children where medication is only the first-line treatment for severe ADHD; the guidelines recommend that other preschoolers with ADHD be treated with non-pharmacologic treatments, when available. You can learn more about non-pharmacologic treatments for ADHD from a book I recently edited: Faraone, S. V. &Antshel, K. M. (2014). ADHD: Non-Pharmacologic Interventions. Child AdolescPsychiatr Clin N Am 23, xiii-xiv.
Background:
Recent progress in reproductive medicine has increased the number of children conceived via assisted reproductive techniques (ART). These include:
Although ART helps with infertility, there are concerns about its long-term effects on offspring, especially regarding neurodevelopment. Factors such as hormonal treatments, gamete manipulation, altered embryonic environments, as well as parental age and infertility, may influence brain development and raise the risk of neurodevelopmental and mental health disorders.
With previous studies finding conflicting results on a possible association between ART and increased risk of mental health disorders, an Indian research team has just published a new meta-analysis exploring this topic.
The Study:
Studies were eligible if they were observational (cohort, case-control, or cross-sectional), reported confounder-adjusted effect sizes for ADHD, and were published in English in peer-reviewed journals.
A meta-analysis of eight studies encompassing nearly twelve million individuals indicated a 7% higher prevalence of ADHD in offspring conceived via IVF/ICSI compared to those conceived naturally. The heterogeneity among studies was minimal, and no evidence of publication bias was observed.
The study’s 95% confidence interval ranged from 4% to 10%. Further analysis of five studies comprising almost nine million participants that distinguished outcomes by sex revealed that the increase in ADHD risk among female offspring was not statistically significant. In contrast, the elevated risk in male offspring persisted, though it was marginally significant, with the lower bound of the confidence limit at only 1%.
Results:
A meta-analysis of three studies (1.4 million participants) found a 13% higher rate of ADHD in children conceived via ovulation induction/intrauterine insemination (OI/IUI) compared to natural conception. The effect size, though doubled, remains small. Minimal heterogeneity and no publication bias were observed.
The team concluded, “The review found a small but statistically significant moderate certainty evidence of an increased risk of ADHD in those conceived through ART, compared to spontaneous conception. The magnitude of observed risk is small and is reassuring for parents and clinicians.”
Our Take-Away:
Overall, the meta-analysis points to a small, but measurable increase in ADHD diagnoses among children conceived through ART, but the effect sizes are modest and supported by moderate-certainty evidence. And we must always keep in mind that the researchers who wrote the original articles could not correct for all possible confounds. These findings suggest that while reproductive technologies may introduce slight variation in neurodevelopmental outcomes, the effects are small and uncertain. For families and clinicians, the results are generally reassuring: ART remains a safe and effective avenue to parenthood, and the results of this study should not be viewed as a prohibitive concern. Thoughtful developmental monitoring and open, evidence-based counseling can help ensure that ART-conceived children receive support that caters to their individual needs.
The Background:
Myopia is a growing global health concern linked to conditions like macular degeneration, glaucoma, and retinal detachment. Its prevalence has surged in recent decades; by 2050, an estimated 5 billion people will have myopia. The increase is especially marked in Asia – a survey in Taiwan reports that 84% of students aged 15 to 18 are myopic, with 24% severely affected.
Dopamine is an important neurotransmitter in the retina, involved in eye development, visual signaling, and refractive changes. The dopamine hypothesis, suggesting that retinal dopamine release helps prevent myopia, has emerged as a leading theory of myopia control.
Most studies show ADHD is highly heritable, often involving dopamine system genes. ADHD is strongly associated with dopaminergic abnormalities, especially in dopamine transporter function and release dynamics.
Medications for ADHD, like methylphenidate, atomoxetine, and clonidine, help regulate dopamine to reduce symptoms.
The Study:
Given dopamine’s critical involvement in both ADHD and myopia, a Taiwanese research team hypothesized that medications for ADHD that influence dopaminergic pathways may have a significant effect on myopia risk.
To evaluate this hypothesis, the team conducted a nationwide cohort study using data from Taiwan’s National Health Insurance (NHI) program, which covers 99% of the nation’s 23 million residents and provides access to comprehensive eye care and screenings. Taiwan requires visual acuity screenings beginning at age four, with annual examinations for school-aged children to promote the early detection of visual anomalies such as myopia.
Furthermore, ADHD medication and diagnosis are tracked through compulsory diagnostic codes. This permits an accurate assessment of the effects of dopaminergic medications on myopia risk.
Propensity score allocation using a multivariable logistic regression model was applied to reduce bias from confounding influences, pairing cohorts based on similar scores.
The Results:
Comparing 133,945 individuals with ADHD with an equal number without ADHD, untreated ADHD was associated with a 22% greater risk of myopia.
However, after adjusting for covariates (gender, age, insured premium, comorbidities, location, and urbanization level), the ADHD cohort receiving medication treatment showed a 39% decreased risk of myopia relative to the untreated ADHD cohort.
Narrowing this further to the ADHD cohort receiving dopaminergic medications reduced the risk of myopia by more than half (52%) relative to the untreated ADHD cohort.
Treatment with two dopaminergic medications reduced the risk by well over two-thirds (72%) relative to the untreated ADHD cohort.
There were no significant differences between methylphenidate, atomoxetine, and clonidine. Each reduced risk by about 50%.
The team did not directly compare the ADHD cohort receiving dopaminergic medications with the non-ADHD cohort. But if there were 122 cases of myopia in the ADHD cohort for every 100 cases in the non-ADHD cohort, and dopaminergic medications halved the cases in the ADHD cohort to about 60, that would represent a roughly 40% reduction in myopia risk relative to the non-ADHD cohort.
The team concluded, “our research indicates that pharmacologically treated ADHD children have a reduced risk of myopia. Conversely, untreated ADHD children are at a heightened risk relative to those without ADHD. Moreover, the cumulative effects of ADHD medications were found to notably decrease myopia incidence, emphasizing the protective influence of dopaminergic modulation in these interventions.”
The Take-Away:
Children with untreated ADHD are more likely to develop myopia, but those receiving dopaminergic medications had a substantially lower risk. The findings suggest that ADHD medications may help protect against myopia by boosting dopamine signaling. More research is needed before firmly drawing this conclusion, but this research could open the door to new approaches for preventing myopia in at-risk children.
Background:
ADHD treatment includes medication, behavioral therapy, dietary changes, and special education. Stimulants are usually the first choice but may cause side effects like appetite loss and stomach discomfort, leading some to stop using them. Cognitive behavioral therapy (CBT) is effective but not always sufficient on its own. Research is increasingly exploring non-drug options, such as transcranial direct current stimulation (tDCS), which may boost medication effectiveness and improve results.
What is tDCS?
tDCS delivers a weak electric current (1.0–2.0 mA) via scalp electrodes to modulate brain activity, with current flowing from anode to cathode. Anodal stimulation increases neuronal activity, while cathodal stimulation generally inhibits it, though effects vary by region and neural circuitry. The impact of tDCS depends on factors such as current intensity, duration, and electrode shape. It targets cortical areas, often stimulating the dorsolateral prefrontal cortex for ADHD due to its role in cognitive control. Stimulation of the inferior frontal gyrus has also been shown to improve response inhibition, making it another target for ADHD therapy.
There is an ongoing debate about how effective tDCS is for individuals with ADHD. One study found that applying tDCS to the left dorsolateral prefrontal cortex can help reduce impulsivity symptoms in ADHD, whereas another study reported that several sessions of anodic tDCS did not lead to improvements in ADHD symptoms or cognitive abilities.
New Research:
Two recent meta-analyses have searched for a resolution to these conflicting findings. Both included only randomized controlled trials (RCTs) using either sham stimulation or a waitlist for controls.
Each team included seven studies in their respective meta-analyses, three of which appeared in both.
Both Wang et al. (three RCTs totaling 97 participants) and Wen et al. (three RCTs combining 121 participants) reported very large effect size reductions in inattention symptoms from tDCS versus controls. There was only one RCT overlap between them. Wang et al. had moderate to high variation (heterogeneity) in individual study outcomes, whereas Wen et al. had virtually none. There was no indication of publication bias.
Whereas Wen et al.’s same three RCTs found no significant reduction in hyperactivity/impulsivity symptoms, Wang et al. combined five RCTs with 221 total participants and reported a medium effect size reduction in impulsivity symptoms. This time, there was an overlap of two RCTs between the studies. Wen et al. had no heterogeneity, while Wang et al. had moderate heterogeneity. Neither showed signs of publication bias.
Turning to performance-based tasks, Wang et al. reported a medium effect size improvement in attentional performance from tDCS over controls (three RCTs totaling 136 participants), but no improvement in inhibitory control (five RCTs combining 234 persons).
Wang et al. found no significant difference in adverse events (four RCTs combining 161 participants) between tDCS and controls, with no heterogeneity. Wen et al. found no significant difference in dropout rates (4 RCTs totaling 143 individuals), again with no heterogeneity.
Wang et al. concluded, “tDCS may improve impulsive symptoms and inattentive symptoms among ADHD patients without increasing adverse effects, which is critical for clinical practice, especially when considering noninvasive brain stimulation, where patient safety is a key concern.”
Wen et al. further concluded, “Our study supported the use of tDCS for improving the self-reported symptoms of inattention and objective attentional performance in adults diagnosed with ADHD. However, the limited number of available trials hindered a robust investigation into the parameters required for establishing a standard protocol, such as the optimal location of electrode placement and treatment frequency in this setting. Further large-scale double-blind sham-controlled clinical trials that include assessments of self-reported symptoms and performance-based tasks both immediately after interventions and during follow-up periods, as well as comparisons of the efficacy of tDCS targeting different brain locations, are warranted to address these issues.”
The Take-Away:
Previous studies have shown mixed results on the benefits of this therapy on ADHD. These new findings suggest that tDCS may hold some real promise for adults with ADHD. While the technique didn’t meaningfully shift hyperactivity or impulsivity, it was well-tolerated and showed benefit, especially in self-reported symptoms. However, with only a handful of trials to draw from, it would be a mistake to suggest tDCS as a standard treatment protocol. Larger, well-designed studies are the next essential step to clarify where, how, and how often tDCS works best.
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