May 5, 2023

The Economic Burden of ADHD

ADHD, especially when untreated, impairs patients and creates difficulties in families.  

Although these are the proximal targets of treatment, ADHD also burdens society due, for example, to underemployment and the use of health resources.   A recent study assessed the economic burden using the Danish population registries, researchers, which link medical information with employment, education, crime, and social care registers while maintaining confidentiality. They identified 5,269 adults with adult ADHD who had not been diagnosed with ADHD in childhood and, we can assume, were probably not treated for the disorder. They excluded patients with other psychiatric diagnoses and cases without a same-sex sibling free of any diagnosed psychiatric diagnoses. That left 460 pairs of same-sex siblings, one with an adult with ADHD and the other with no psychiatric diagnosis. They selected the non-ADHD sibling closest in age to the ADHD sibling. Using siblings mitigated the effects of genetics and upbringing between the ADHD group and normally developing controls.

Looking at personal income (combining work income and public transfers), adults with ADHD on average brought home about 12,000 Euros less - almost a third less - than their sibling counterparts. They also paid 40% less tax. Balancing that out, their after-tax income was roughly 7,500 Euros less than their siblings. With the additional personal cost of prescribed medication(prescriptions are relatively inexpensive in Denmark, and co-payments even more so) the net personal cost to adults with ADHD was 7,700 Euros.

The net public costs were considerably greater. That was primarily due to the reduction in taxes paid (about 4,500 Euros) and the increase in income replacement transfers (just over 5,500 Euros). The cost of additional crimes committed by adults with ADHD added another 1,000 Euros. Additional primary and secondary health care costs contributed another 1,000 Euros. Subsidies for prescribed medicines added 661 Euros, but that was partly counterbalanced by a reduction of 344 Euros in education costs. There were no significant differences in costs from traffic accidents or adult continuation of foster care. Overall, the net per capita public cost of adults with ADHD was just over 12,400 Euros each year.

Combining public and private costs, the per capita economic burden of adult ADHD was just over 20,000 Euros each year.

The study could not evaluate the extent to which ADHD treatment may reduce the economic burden, but given many studies that show treatment for ADHD reduces impairments, we would expect treatment to have a positive impact on the economic burden.  These results are extremely important for policymakers and for those who control the allocation of treatment in healthcare systems.  Although treating ADHD incurs costs, not treating it incurs even greater costs in the long run

D. Daley, R.H. Jacobsen, A.-M. Lange, A. Sørensen, J.Walldorf, "The economic burden of adult attention-deficit hyperactivity disorder: A sibling comparison cost analysis," European Psychiatry61(2019) 41-48.

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Updates on ADHD and Vitamin D

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. 

July 28, 2025

What Metabolites Tell Us About ADHD — And What This Means for Diet and Treatment

New research has uncovered important links between certain blood metabolites and ADHD by using a genetic method called Mendelian randomization. This approach leverages natural genetic differences to help identify which metabolites might actually cause changes in ADHD risk, offering stronger clues than traditional observational studies.

Key Metabolic Pathways Involved:

The study found 42 plasma metabolites with a causal relationship to ADHD. Most fall into two major groups:

  • Amino acid metabolites from protein metabolism, including those related to tyrosine, methionine, cysteine, and taurine.

  • Fatty acids, especially long-chain polyunsaturated fatty acids (PUFAs) like DHA and EPA, important for brain function.

What Does This Mean for Diet and ADHD?

Since many metabolites come from dietary sources like proteins and fats this supports the idea that diet could influence metabolic pathways involved in ADHD. However, because the study focused on genetic influences on metabolite levels, it doesn’t directly prove that dietary changes will have the same effects.

Notable Metabolites:

  • 3-Methoxytyramine sulfate (MTS): linked to dopamine metabolism, higher genetic levels of MTS were associated with a lower risk of ADHD. Dopamine plays a crucial role in attention and behavior.

  • DHA and EPA: Omega-3 fatty acids abundant in the brain; higher levels were linked to reduced ADHD risk, supporting existing research on omega-3 supplements.

  • N-acetylneuraminate: Involved in brain development and immune function, with higher levels linked to increased ADHD risk, though more research is needed to understand this.

Five metabolites showed bidirectional links with ADHD, meaning genetic risk for ADHD also affects their levels which suggests a complex interaction between brain function and metabolism.

Twelve ADHD-related metabolites are targets of existing drugs or supplements, including:

  • Acetylcysteine: an antioxidant used in various treatments.

  • DHA supplements: widely used to support brain and heart health.

What This Study Doesn’t Show

While these findings highlight biological pathways, they don’t prove that changing diet will directly alter ADHD symptoms. Metabolite levels are shaped by genetics plus environment, lifestyle, and health factors, which require further study.

Conclusion: 

This research provides stronger evidence of metabolic pathways involved in ADHD and points to new possibilities for diagnosis and treatment. Future work could explore how diet or drugs might safely adjust these metabolites to help manage ADHD.

While this study strengthens the link between amino acid and fatty acid metabolism and ADHD risk, suggesting that diet could play a role, ultimately more research is still needed before experts could use this research to give specific nutritional advice.

July 21, 2025

Network Meta-analysis Explores Long-term Efficacy of Nonpharmacological Treatments for Improving Inhibitory Control in Children and Adolescents with ADHD

Background Info:

Executive functions include inhibitory control, working memory, and cognitive flexibility. Inhibitory control is the ability to suppress distractions and focus on goals, which is the main deficit in ADHD. 

Children and adolescents with ADHD often have off-task, unrelated thoughts and are easily distracted, limiting their sustained attention. This makes it difficult for them to focus on tasks and leads to impulsive behaviors that affect their daily life, academics, and social interactions. Improving inhibitory control in ADHD children and adolescents is essential. 

Stimulant medications are commonly used to treat ADHD. However, side effects like insomnia, loss of appetite, and headaches may make parents hesitant to use these medications for their children. 

Non-pharmacological treatments like cognitive training, behavior therapy, and physical exercise have gained attention for their lack of side effects. Research shows that some non-pharmacological methods can improve cognitive outcomes significantly, underscoring their potential in treating ADHD. 

Study:

A Chinese research team identified four key gaps in current research on non-pharmacological treatments for inhibitory control in children with ADHD: 

  • Existing meta-analyses seldom differentiate between short-term and long-term interventions.  
  • Most studies focus primarily on short-term effects and neglect evaluation of maintenance effects through follow-up assessments.  
  • New treatment methods, such as meditation and board games, have not been systematically assessed in meta-analyses for their impact on inhibitory control in children and adolescents with ADHD, leaving their effectiveness uncertain.  
  • Traditional meta-analysis does not tell us which intervention is most effective. Without this comparative analysis, it is difficult to rank efficacy. 

The team therefore performed a network meta-analysis of long-term randomized controlled trials (RCTs) to assess and rank the effectiveness of various non-pharmacological treatments on inhibitory control in children and adolescents with ADHD. 

The team included only RCTs relying on professional diagnoses of ADHD, excluding those based only on parent and teacher rating scales.  

The included studies measured inhibitory control using objective neurocognitive tasks, such as the Stroop test and the Go/No-Go test, to reduce potential subjective bias. Studies relying on parent- or teacher-reported questionnaires were excluded. 

Controls either received no intervention or placebo, such as watching running videos and attending history classes. 

Meta-analysis of 16 studies combining 546 participants found large short-term effect size improvements in inhibitory control from physical exercise. But the two studies with a total of 110 participants that performed a follow-up test reported only a small-to-medium effect size improvement. 

For cognitive training, a meta-analysis of fifteen studies totaling 674 participants reported a medium effect size of short-term improvement in inhibitory control. The ten studies with 563 participants that performed a follow-up test found only a small effect size improvement since treatment initiation. 

For behavioral therapy, meta-analysis of six studies encompassing 244 individuals likewise found a medium effect size short-term improvement in inhibitory control. In this case, however two studies combining 91 participants that performed a follow-up test reported that the medium effect size improvement was maintained. 

For neurofeedback, meta-analysis of seven studies encompassing 186 individuals found a small-to-medium effect size short-term improvement in inhibitory control. The only study that performed a follow-up test reported a small effect size improvement since treatment initiation. 

The two studies with a combined 44 individuals exploring board games found no significant improvement in inhibitory control. Likewise, the two studies combining 32 participants that explored meditation found no significant improvement in inhibitory control. 

There was no indication of publication bias. 

Conclusion:

The team concluded, “Existing evidence shows that physical exercise, behavior therapy, cognitive training, and neurofeedback can effectively improve the inhibitory control of children and adolescents with ADHD. However, meditation, EMG feedback, and board games did not significantly affect inhibitory control. Physical exercise has the best effect among all non-pharmacological treatments, but its impact will be weakened after intervention. Behavior therapy and cognitive training had a slightly lower effect, but they have a better maintenance effect.” 

Ultimately, the study results suggest that non-drug treatments can help children and teens with ADHD improve their ability to control their actions and stay focused. Some methods, like physical exercise, work well at first but may fade once the activity stops. Other methods, like behavioral therapy and cognitive training, may take a little longer to show results but can last longer and make a bigger difference over time. Ultimately, and most importantly, because this work did not study the symptoms of ADHD or its real-world impairments, it provides no reason to change current treatment practices for ADHD.

July 16, 2025