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October 15, 2025

Yes, ADHD Diagnoses Are Rising, But That Doesn’t Mean It’s Overdiagnosed

Many news outlets have reported an increase – or surge – in attention-deficit/hyperactivity disorder, or ADHD, diagnoses in both children and adults. At the same time, health care providers, teachers and school systems have reported an uptick in requests for ADHD assessments.

These reports have led some experts and parents to wonder whether ADHD is being overdiagnosed and overtreated.

As researchers who have spent our careers studying neurodevelopmental disorders like ADHD, we are concerned that fears about widespread overdiagnosis are misplaced, perhaps based on a fundamental misunderstanding of the condition.

Understanding ADHD as a spectrum:

Discussions about overdiagnosis of ADHD imply that you either have it or you don’t.

However, when epidemiologists ask people in the general population about their symptoms of ADHD, some have a few symptoms, some have a moderate level, and a few have lots of symptoms. But there is no clear dividing line between those who are diagnosed with ADHD and those who are not, since ADHD – much like blood pressure – occurs on a spectrum.

Treating mild ADHD is similar to treating mild high blood pressure – it depends on the situation. Care can be helpful when a doctor considers the details of a person’s daily life and how much the symptoms are affecting them.

Not only can ADHD symptoms be very different from person to person, but research shows that ADHD symptoms can change within an individual. For example, symptoms become more severe when the challenges of life increase.

ADHD symptoms fluctuate depending on many factors, including whether the person is at school or home, whether they have had enough sleep, if they are under a great deal of stress or if they are taking medications or other substances. Someone who has mild ADHD may not experience many symptoms while they are on vacation and well rested, for example, but they may have impairing symptoms if they have a demanding job or school schedule and have not gotten enough sleep. These people may need treatment for ADHD in certain situations but may do just fine without treatment in other situations.

This is similar to what is seen in conditions like high blood pressure, which can change from day to day or from month to month, depending on a person’s diet, stress level and many other factors.

Can ADHD symptoms change over time?

ADHD symptoms start in early childhood and typically are at their worst in mid-to late childhood. Thus, the average age of diagnosis is between 9 and 12 years old. This age is also the time when children are transitioning from elementary school to middle school and may also be experiencing changes in their environment that make their symptoms worse.

Classes can be more challenging beginning around fifth grade than in earlier grades. In addition, the transition to middle school typically means that children move from having all their subjects taught by one teacher in a single classroom to having to change classrooms with a different teacher for each class. These changes can exacerbate symptoms that were previously well-controlled. Symptoms can also wax and wane throughout life.

Psychiatric problems that often co-occur with ADHD, such as anxiety or depression, can worsen ADHD symptoms that are already present. These conditions can also mimic ADHD symptoms, making it difficult to know which to treat. High levels of stress leading to poorer sleep, and increased demands at work or school, can also exacerbate or cause ADHD-like symptoms.

Finally, the use of some substances, such as marijuana or sedatives, can worsen, or even cause, ADHD symptoms. In addition to making symptoms worse in someone who already has an ADHD diagnosis, these factors can also push someone who has mild symptoms into full-blown ADHD, at least for a short time.

The reverse is also true: Symptoms of ADHD can be minimized or reversed in people who do not meet full diagnostic criteria once the external cause is removed.

How prevalence is determined:

Clinicians diagnose ADHD based on symptoms of inattention, hyperactivity and impulsivity. To make an ADHD diagnosis in children, six or more symptoms in at least one of these three categories must be present. For adults, five or more symptoms are required, but they must begin in childhood. For all ages, the symptoms must cause serious problems in at least two areas of life, such as home, school or work.

Current estimates show that the strict prevalence of ADHD is about 5% in children. In young adults, the figure drops to 3%, and it is less than 1% after age 60. Researchers use the term “strict prevalence” to mean the percentage of people who meet all of the criteria for ADHD based on epidemiological studies. It is an important number because it provides clinicians and scientists with an estimate on how many people are expected to have ADHD in a given group of people.

In contrast, the “diagnosed prevalence” is the percentage of people who have been diagnosed with ADHD based on real-world assessments by health care professionals. The diagnosed prevalence in the U.S. and Canada ranges from 7.5% to 11.1% in children under age 18. These rates are quite a bit higher than the strict prevalence of 5%.

Some researchers claim that the difference between the diagnosed prevalence and the strict prevalence means that ADHD is overdiagnosed.

We disagree. In clinical practice, the diagnostic rules allow a patient to be diagnosed with ADHD if they have most of the symptoms that cause distress, impairment or both, even when they don’t meet the full criteria. And much evidence shows that increases in the diagnostic prevalence can be attributed to diagnosing milder cases that may have been missed previously. The validity of these mild diagnoses is well-documented.

Consider children who have five inattentive symptoms and five hyperactive-impulsive symptoms. These children would not meet strict diagnostic criteria for ADHD even though they clearly have a lot of ADHD symptoms. But in clinical practice, these children would be diagnosed with ADHD if they had marked distress, disability or both because of their symptoms – in other words, if the symptoms were interfering substantially with their everyday lives.

So it makes sense that the diagnosed prevalence of ADHD is substantially higher than the strict prevalence.

Implications for patients, parents and clinicians:

People who are concerned about overdiagnosis commonly worry that people are taking medications they don’t need or that they are diverting resources away from those who need it more. Other concerns are that people may experience side effects from the medications, or that they may be stigmatized by a diagnosis.

Those concerns are important. However, there is strong evidence that underdiagnosis and undertreatment of ADHD lead to serious negative outcomes in school, work, mental health and quality of life.

In other words, the risks of not treating ADHD are well-established. In contrast, the potential harms of overdiagnosis remain largely unproven.

It is important to consider how to manage the growing number of milder cases, however. Research suggests that children and adults with less severe ADHD symptoms may benefit less from medication than those with more severe symptoms.

This raises an important question: How much benefit is enough to justify treatment? These are decisions best made in conversations between clinicians, patients and caregivers.

Because ADHD symptoms can shift with age, stress, environment and other life circumstances, treatment needs to be flexible. For some, simple adjustments like classroom seating changes, better sleep or reduced stress may be enough. For others, medication, behavior therapy, or a combination of these interventions may be necessary. The key is a personalized approach that adapts as patients’ needs evolve over time.

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Exploring the Impact of ADHD Treatment on Empathy and Narcissism

A recent study published in Alpha Psychiatry sheds light on the connection between ADHD, empathy, and narcissistic traits. Researchers aimed to evaluate how pharmacological treatments—specifically psychostimulants—affect empathy deficits and pathological narcissism in adults with ADHD. These findings could have important implications for enhancing treatment outcomes and improving social functioning.

Study Overview:
The study involved 75 adult ADHD patients who were treated with either methylphenidate or atomoxetine. Researchers assessed levels of narcissistic traits and empathy using validated tools such as the Pathological Narcissism Inventory (PNI) and the Empathy Quotient (EQ). Measurements were taken before treatment and after three months of therapy.

Key Findings:

  • Narcissistic Traits: Patients showed a significant reduction in grandiosity and vulnerability scores, with total PNI scores decreasing after treatment.
  • Empathy Levels: Empathy improved significantly, as reflected by higher post-treatment EQ scores.
  • Overall Impact: These changes suggest that psychostimulant treatment positively influences brain circuits related to empathy and narcissistic tendencies, potentially leading to better interpersonal relationships.

Why It Matters:
Adults with ADHD often struggle with social interactions, partly due to empathy deficits and personality traits like narcissism. By addressing these challenges through psychostimulant treatment, patients may experience better social and emotional well-being. This study underscores the importance of viewing ADHD treatment as not just a way to manage symptoms but also a means to improve overall quality of life.

Takeaway
Effective ADHD treatment goes beyond managing attention and hyperactivity. By improving empathy and reducing narcissistic traits, psychostimulants can foster healthier relationships and enhance social functioning. This research highlights the need for comprehensive care that considers the broader psychological and interpersonal effects of ADHD.

February 4, 2025
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Meta-analysis Suggests Music Training May Be a Useful Tool for Inhibition Control

According to Fosco et al. (2019), “Inhibitory control has long been considered a central neurocognitive process in ADHD, with ADHD groups typically showing medium-sized impairments relative to their typically-developing peers on common inhibition paradigms.” 

Learning to play a musical instrument requires effective coordination of physical movements and sound signals to produce music. Musical training involves repetitive practice, perfecting connections between perceptions, muscular actions, and cognition. 

Noting that listening to music activates the brain’s reward circuits in both children and adults, that “Being internally motivated during learning experiences increases learning capacity and efficiency, and this greater engagement is reflected in increased electrical brain activity following musical training,” and that “Training music in a social environment increases positive feelings of bonding through shared emotions and group synchrony,” a Montreal-based research team carried out a systematic review and meta-analysis of the peer-reviewed medical literature from 1980 to 2023 to learn what effect music training might have on inhibition control. 

Outcomes:

The team found eight randomized controlled trials (RCTs) and 14 other longitudinal studies that met search criteria, including: 

  • Music training was with neurotypical children and adolescents 
  • The experimental group was trained using music alone 
  • Studies were longitudinal, with either active or passive controls 
  • Studies included a performance-based inhibition control measure as an outcome 

Meta-analysis of all 22 longitudinal studies with a combined total of 1,734 participants yielded a small-to-medium effect size improvement in inhibitory control. Variation (heterogeneity) in outcomes between individual studies was small, and there was no sign of publication bias. Restricting the analysis to the eight RCTs with a combined total of 641 participants, however, yielded a medium-to-large effect size improvement, with negligible heterogeneity, meaning the outcome was consistent across RCTs. 

The Take-Away: The team concluded, “Music training plays a privileged role compared to other activities (sports, visual arts, drama) in improving children’s executive functioning, with a particular effect on inhibition control.”   I cannot, however, recommend this as a therapy for ADHD until RCTs show it reduces symptoms of ADHD and/or real world impairments associated with the disorder.

February 3, 2025
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Population Study Finds No ADHD- or ASD- Related Benefits From Eating Organic Food During Pregnancy

Norwegian Nationwide Population Study Finds No ADHD- or ASD- Related Benefits From Eating Organic Food During Pregnancy

Background:

Organic farming aims to protect biodiversity, promote animal welfare, and avoid using pesticides and fertilizers made from petrochemicals. Some pesticides are designed to target insects’ nervous systems but can also affect brain development and health in larger animals, including humans.

Many people believe organic food is healthier than conventionally produced food, which might be true for certain foods and health factors. But does eating organic food during pregnancy impact the chances of a child developing ADHD or autism spectrum disorder (ASD)?

In Norway, researchers can use detailed national health records to study these connections on a population-wide level, thanks to the country’s single-payer healthcare system and national registries.

Method:

The Norwegian Mother, Father, and Child Cohort Study (MoBa) invites parents to participate voluntarily and has a 41% participation rate. The study includes:

  • 114,500 children
  • 95,200 mothers
  • 75,200 fathers

For this research, a team tracked 40,707 mother-child pairs from children born between 2002 and 2009. They used questionnaires to measure how much organic food mothers consumed during pregnancy. ADHD and ASD symptoms in children were assessed using validated rating scales.

The final analysis included:

  • 40,586 pairs for ADHD symptoms
  • 40,117 pairs for ASD symptoms

The researchers adjusted for factors like maternal age, education, previous pregnancies, BMI before pregnancy, smoking and alcohol use during pregnancy, birth year and season, and the child’s sex.

Key Findings:
  • There was a weak connection between higher organic food consumption and fewer ADHD symptoms in children. However, this link disappeared when maternal ADHD symptoms were considered (31,411 pairs) or when the analysis was limited to siblings (5,534 pairs).
  • Similarly, weak associations between organic food and fewer ASD symptoms disappeared when focusing on siblings (4,367 pairs).
Conclusion:

The researchers concluded that eating organic food during pregnancy has no meaningful effect on the likelihood of a child developing ADHD or ASD. They stated, “The results do not indicate any clinically significant protective or harmful effects of eating organic food during pregnancy on symptoms of ADHD and ASD in the offspring. Based on these findings, we do not recommend any specific advice regarding intake of organic food during pregnancy.”

January 27, 2025
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Meta-analysis Finds Little or No Link Between Assisted Reproductive Technologies and ADHD

Background:

Infertility affects about one in six couples worldwide. To address this, medical experts have developed Assisted Reproductive Technologies (ART), including In Vitro Fertilization (IVF) with or without Intra-Cytoplasmic Sperm Injection (ICSI).

Some research suggests that children conceived through ART might have higher rates of intellectual disabilities, cerebral palsy, cancer, and neurological issues compared to children conceived naturally. However, studies looking at a possible link between ART and ADHD have produced mixed and conflicting results.

Until now, there hasn’t been a meta-analysis examining the connection between ART and ADHD. A South Korean research team has conducted the first systematic review and meta-analysis on this topic. Their final analysis included eight studies with a total of over ten million participants, comprising six cohort studies and two cross-sectional studies.

Method:

The research focused on two types of studies:

  1. Cohort Studies: These follow two groups (one exposed to ART and one not exposed) over time to see if a specific outcome, like ADHD, occurs.
  2. Cross-Sectional Studies: These compare the prevalence of ADHD at a single point in time between those exposed to ART and those who weren’t.

Both types of studies are observational, meaning they don’t involve controlled experiments and can be influenced by confounding factors.  So they can document interesting associations, not causality.  The studie were mostly large-scale national studies and used clinical ADHD diagnoses.

Key Findings:
  • Cohort Studies: Meta-analysis of six cohort studies, involving nearly 8 million participants, found no link between ART and ADHD. However, there was high variability (heterogeneity) in the results from individual studies.
  • Cross-Sectional Studies: Meta-analysis of two cross-sectional studies, covering over 2.3 million participants, also found no link between ART and ADHD. Heterogeneity was moderate.
  • Adjustment for Confounding: A separate analysis of three studies that adjusted for confounding factors (like socioeconomic status or parental health) involved more than 7.5 million participants. It found a very small association, with ART-conceived children being 8% more likely to develop ADHD. There was no variability among these studies.
Conclusion:

The researchers concluded that while there may be a small association between ART and ADHD, the effect is minimal, and the results are influenced by differences in study designs. They advised interpreting these findings with caution, noting, “The limited effect size and inherent heterogeneity underscore the need for cautious interpretation.”

January 24, 2025
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Taiwan nationwide population study documents link between ADHD and periodontitis in adolescents

Population Study Documents Link Between ADHD and Periodontitis in Adolescents

Background:

Periodontitis, commonly known as gum disease, is a condition where the gums become inflamed. If untreated, it can cause the gums to pull back from the teeth, exposing their base, which may eventually lead to loose teeth or tooth loss. While this condition mostly affects adults, it’s also common among teens who don’t floss or brush their teeth properly.

Until now, only a few small studies have looked at a possible link between ADHD and gum disease. A team in Taiwan recently conducted a nationwide study to explore this connection.

Taiwan has a universal health insurance program, introduced in 1995, that provides medical care to nearly all (99.7%) residents. The Taiwan National Health Research Database collects and oversees all insurance claims, making it an excellent resource for large-scale studies.

Methods:

The researchers used the database to identify teens aged 12 to 19 with ADHD (diagnosed by a psychiatrist) who had no history of gum disease between 2001 and 2011. These teens made up the ADHD group. They matched each ADHD participant with four teens who didn’t have ADHD or gum disease, creating a control group. The groups were matched by age, gender, enrollment date, family income, place of residence, and other health conditions (like obesity, diabetes, smoking, depression, and substance use).

All diagnoses of gum disease were confirmed by board-certified dentists.

The study included:

  • 16,211 teens with ADHD
  • 162,110 matched controls
Key Findings:
  • Teens with ADHD were 2.3 times more likely to develop gum disease than those in the control group without ADHD.
  • There were no significant differences between boys and girls or among teens from different income levels (low, medium, or high).
  • ADHD medications, mainly methylphenidate, didn’t affect the likelihood of developing gum disease. This was true for both short-term and long-term users compared to non-users.
Conclusion:

The researchers concluded that teens with ADHD have a higher risk of developing gum disease later on, even after accounting for other risk factors like smoking, diabetes, and depression. They stated, “ADHD is an independent risk factor for developing periodontitis.”

January 23, 2025
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Meta-Analysis: Physical Activity for Children and Adolescents with ADHD

Attention Deficit Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental disorder that significantly impacts children’s academic performance, social interactions, and overall quality of life (QoL). While medication is the standard treatment, it often comes with side effects and may not always provide sufficient benefits. A new systematic review and meta-analysis aims to investigate whether physical activity can offer a viable and effective alternative or complement to medication.

About the Study
This protocol, developed in line with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA) guidelines, focuses on randomized clinical trials involving children and adolescents (ages 3–18) diagnosed with ADHD or hyperkinetic disorder. The study's goal is to evaluate the effects of physical activity on:

  • Quality of life (QoL)
  • Executive functions
  • ADHD symptoms
  • Functional impairments

Unlike earlier reviews, which often included non-randomized trials or imposed limits on activity types, this analysis takes a more robust and inclusive approach. It is the first of its kind to examine QoL as an outcome while also incorporating trial sequential analysis—a method to assess evidence strength over time.

Why Physical Activity?
Physical activity is believed to impact the same brain systems targeted by ADHD medications, particularly the catecholaminergic system. This overlap suggests that exercise could play a key role in managing symptoms, potentially reducing reliance on medication or enhancing its effects.

Methodology Highlights

  • The review will adhere to principles outlined in the Cochrane Handbook for Systematic Reviews of Interventions.
  • It incorporates the latest research and focuses on randomized trials to ensure high-quality evidence.
  • No restrictions are placed on the frequency or intensity of physical activity interventions, making the findings broadly applicable.

Significance and Dissemination
The results of this systematic review will provide critical insights into how physical activity could improve outcomes for children and adolescents with ADHD. It is also notable as the first review in this field to prioritize quality of life—a crucial, often-overlooked measure of treatment success.

The findings will be published in peer-reviewed journals and presented at relevant conferences to inform clinicians, educators, and families.

Conclusion
As concerns about the limitations of ADHD medication grow, exploring alternatives like physical activity becomes increasingly important. This systematic review has the potential to shape future treatment strategies, offering children with ADHD a chance for better symptom management and a higher quality of life.

January 21, 2025
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NEW STUDY: Understanding the Gap Between ADHD Clinical Trials and Real-World Patients

Background 

ADHD (Attention-Deficit/Hyperactivity Disorder) is one of the most studied neurodevelopmental conditions, with many clinical trials evaluating the effectiveness and safety of various medications. These trials, known as randomized controlled trials (RCTs), are considered the gold standard for assessing treatments. However, strict eligibility criteria often exclude many real-world patients, raising questions about whether the findings from these trials apply to everyday clinical settings.

Our latest study sheds light on this issue, revealing just how many individuals with ADHD might be excluded from RCTs and the impact this exclusion has on their treatment outcomes. 

Method

Researchers used Swedish national registries to analyze data from 189,699 individuals diagnosed with ADHD who started medication between 2007 and 2019. They applied exclusion criteria from 164 international RCTs to identify who would have been considered ineligible for these trials in order to determine the proportion of individuals with ADHD who would not meet the eligibility criteria for RCTs.  

Key Findings

Many Patients Are Ineligible for Clinical Trials:

  • Over half (53%) of the study population would have been ineligible for ADHD medication trials.
  • Adults were most likely to be excluded (74%), followed by adolescents (35%) and children (21%).

Ineligible Patients Face Unique Challenges:

  • Treatment Switching: Ineligible individuals were more likely to switch medications within the first year (14% higher likelihood compared to eligible patients).
  • Medication Discontinuation: They were slightly less likely to stop taking their medication during the first year.

Higher Risk of Adverse Outcomes:

  • Ineligible patients experienced significantly higher rates of psychiatric hospitalizations and health issues such as depression, anxiety, and substance use disorders. For instance:
    • Psychiatric hospitalizations: Nearly 10 times more likely.
    • Specialist visits for substance use disorders: About 15 times more likely.
    • Anxiety-related visits: Over 11 times more likely.

What This Means

These findings highlight a major gap between the controlled environments of clinical trials and the realities faced by individuals with ADHD in everyday life. While RCTs provide valuable insights, their restrictive criteria often exclude patients with more complex health profiles or co-existing conditions. This limits the generalisability of trial results, meaning that treatment guidelines based solely on RCTs may not fully address the needs of all patients.

Conclusion

This study demonstrated that a significant proportion of individuals with ADHD, particularly adults, do not meet the eligibility criteria for standard RCTs. These results emphasize the importance of bridging the gap between research settings and real-world applications. By recognizing and addressing the limitations of RCTs, we can work towards more equitable and effective ADHD treatment strategies for everyone.

January 14, 2025
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Where Does ADHD Fit in the Psychopathology Hierarchy? A Symptom-Focused Study

NEWS TUESDAY: Where Does ADHD Fit in the Psychopathology Hierarchy? A Symptom-Focused Study

Background:

Our understanding of Attention-deficit/hyperactivity disorder (ADHD) has grown and evolved considerably since it first appeared in the DSM-II as “Hyperkinetic Reaction of Childhood.”  This study aimed to find the disorder’s placement within the modern psychopathology classification systems like the Hierarchical Taxonomy Of Psychopathology (HiTOP). 

The HiTOP model aims to address limitations of traditional classification systems for mental illness, such as the DSM-5 and ICD-10, by organizing psychopathology according to evidence from research on observable patterns of mental health problems.. Is ADHD best categorized under externalizing conditions, neurodevelopmental disorders, or something else entirely? A recent study by Zheyue Peng, Kasey Stanton, Beatriz Dominguez-Alvarez, and Ashley L. Watts takes a closer look at this question using a symptom-focused approach.

The Study:

Traditionally, ADHD has been associated with externalizing behaviors, such as impulsivity and hyperactivity, or with neurodevelopmental traits, like cognitive delays. However, this study challenges the idea of placing ADHD into a single category. Instead, it maps ADHD symptoms across three major psychopathology spectra: externalizing, neurodevelopmental, and internalizing.

The findings reveal that ADHD symptoms don’t fit neatly into one box. For example, symptoms like impulsivity, poor school performance, and low perseverance were strongly associated with externalizing behaviors. On the other hand, cognitive disengagement (e.g., daydreaming, blank staring) and immaturity were closely linked to neurodevelopmental challenges. Interestingly, cognitive disengagement also showed ties to internalizing symptoms, such as anxiety or depression.

This research underscores the complexity of ADHD. Rather than treating ADHD as a single, unitary construct, the study advocates for a symptom-based approach to better understand and treat individuals. By acknowledging that ADHD symptoms relate to multiple psychopathology spectra, clinicians and researchers can move toward more nuanced classification systems and targeted interventions.

Conclusion: 

Ultimately, this study highlights the need for modern systems to move beyond rigid categories and adopt a more flexible, symptom-focused framework for understanding ADHD’s place in psychopathology.

January 6, 2025
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Meta-analyses Find Dose-response Association Between Lead Exposure and Subsequent ADHD

Meta-analyses Find Dose-response Association Between Lead Exposure and Subsequent ADHD

Background:

Exposure to heavy metals like lead, arsenic, mercury, cadmium, and manganese is known to harm developing nervous systems. However, past studies on whether heavy metals specifically increase the risk of ADHD have shown mixed results.

A research team from China (Gu et al., 2024) reviewed medical studies and conducted meta-analyses to better understand this issue.

Methods:

The team included studies on children and teens, focusing on cohort studies, case-control studies, and cross-sectional studies. They only used articles written in English and required validated biomonitoring (like blood tests) to measure heavy metal exposure. ADHD diagnoses had to come from clinical evaluations.

To be included, studies had to report effect sizes such as odds ratios and relative risks with confidence intervals. The team focused on comparisons between groups with high, low, or no exposure, which made it harder to analyze dose-response relationships.

They also evaluated the quality of each study. All cohort studies were rated high-quality. Of the 15 case-control studies, 6 were high-quality, and 9 were moderate-quality. Among cross-sectional studies, only 2 were high-quality, and the rest were moderate-quality.

Key Findings:
  1. Lead Exposure and ADHD:some text
    • A meta-analysis of 22 studies with over 20,000 participants found that early exposure to lead was linked to about twice the odds of an ADHD diagnosis compared to unexposed children.
    • However, results varied widely among studies, and signs of publication bias were detected. After adjusting for this bias, the increased odds dropped to about 50%.
    • A dose-response relationship was found:some text
      • Blood lead levels of 2.5 µg/dL increased ADHD risk by 1.8 times.
      • Levels of 5 µg/dL increased the risk 2.5 times.
      • Levels of 7.5 µg/dL increased the risk 2.75 times.
      • Levels of 10 µg/dL tripled the risk.
  2. Other Metals:some text
    • No significant links were found between ADHD and exposure to arsenic, mercury, cadmium, or manganese. Fewer studies were available for these metals, and participant numbers were much smaller:some text
      • Arsenic exposure: 25% higher odds of ADHD (4 studies, 3,116 participants).
      • Mercury exposure: 25% higher odds (6 studies, 2,916 participants).
      • Cadmium exposure: 25% higher odds (5 studies, 2,419 participants).
      • Manganese exposure: 45% higher odds (6 studies, 1,664 participants).
  3. Austrian Study: An Austrian team (Rosenauer et al., 2024) also conducted a meta-analysis on lead exposure and ADHD. They included 14 studies with over 7,600 participants and found:some text
    • Lead exposure increased the odds of ADHD by about 25%.
    • Studies focusing on higher lead levels found a 43% increased risk, supporting a dose-response relationship.
    • Study results were consistent, with no signs of publication bias.
Conclusion:

There was no evidence linking ADHD to other heavy metals like arsenic, mercury, cadmium, or manganese.  Both meta-analyses suggest that lead exposure is associated with the risk for ADHD.  However, because these studies cannot rule out other explanations, one cannot conclude that lead exposure causes ADHD.  For example, other work shows that people with ADHD are likely to have lower incomes than those without ADHD.  

January 17, 2025
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No Link Found Between Maternal Coffee Consumption and Subsequent Neurodevelopmental Difficulties

Norwegian nationwide population study finds no link between maternal coffee consumption during pregnancy and offspring neurodevelopmental difficulties, including ADHD

The Background:

Caffeine and its primary breakdown compounds – paraxanthine, theophylline, and theobromine (also the primary alkaloid in chocolate) – readily cross the placenta and tend to linger due to the underdevelopment of fetal caffeine metabolizing enzymes.

Could accumulating caffeine metabolites harm the developing fetal brain? Studies to date have come to contradictory conclusions, some finding an association, others finding none.

Norway has a national single-payer health insurance system with a national health registry comprehensively tracking virtually all residents.

The Methods:

An international study team used Norways’s registry, and its Mother, Father, and Child Cohort Study (MoBa) to explore the relationship between maternal and paternal coffee consumption and offspring neurodevelopmental difficulties (ND), including symptoms of ADHD as determined from validated rating scales, using 58,964 mother-child pairs and 22,576 father-child pairs, covering the decade 1999-2008.

Unadjusted results indicated a strong association between maternal coffee consumption before and during pregnancy with offspring ADHD, but none with paternal coffee consumption. Superficially, that might seem like compelling evidence.

Yet after adjusting for education, income, smoking, and alcohol, “previously significant effects attenuated towards zero and some associations switched from being positive to negative.”

Then, after further adjusting for genetic confounding, ADHD symptoms at 1.5 years, 3 years, 5 years (on both of two different rating scales), and 8 years (including separate measures of inattention and hyperactivity symptoms) all became indistinguishable between offspring from mothers consuming coffee during pregnancy and offspring of mothers abstaining from coffee during pregnancy. 

Conclusion:

The team concluded, “This study applied several conventional and genetic epidemiological approaches to investigate the potential relationship between maternal coffee consumption during pregnancy and offspring NDs [neurodevelopmental difficulties]. When considering the results of the conventional and genetic epidemiological analyses, as well as the broader literature, we conclude that there is little evidence that maternal coffee consumption during pregnancy is strongly causally related to offspring NDs.”

More specifically, the team found no evidence of any causal relationship with offspring ADHD

January 2, 2025
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