June 18, 2024

NEW STUDY: The Cumulative Impact of ADHD, ASD, and Intellectual Disabilities

Neurodevelopmental conditions often coexist, creating a complex web of challenges for affected individuals. A recent study by Hollingdale et al. delves into the cumulative effects of attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and intellectual disability (ID) on young people’s behavioral and socio-emotional well-being, as well as their overall functioning as rated by clinicians.

The researchers conducted a cross-sectional analysis of 2768 young individuals aged 3-17 years, with a mean age of approximately 11.5 years. Diagnostic information along with caregiver-rated behavioral and socio-emotional data, and clinician-rated functioning scores, were collected from electronic patient records at the point of initial diagnosis.

The study aimed to understand whether the number of neurodevelopmental conditions—ranging from one to three—correlates with more pronounced behavioral and socio-emotional issues, and lower levels of clinician-rated functioning. The behavioral and socio-emotional aspects were assessed using the Strengths and Difficulties Questionnaire, while the Children's Global Assessment Scale was used to evaluate clinician-rated functioning.

The findings revealed that young people with multiple neurodevelopmental conditions tend to exhibit higher levels of inattention and hyperactivity, greater peer-related problems, reduced prosocial behaviors, and poorer overall functioning. Interestingly, this cumulative impact was more evident in males compared to females, with females only showing significant cumulative effects in clinician-rated functioning.

This research underscores the importance of recognizing the compounded difficulties faced by young people with multiple neurodevelopmental conditions. It highlights the need for tailored interventions that address the unique and overlapping challenges presented by ADHD, ASD, and ID. For practitioners, understanding these cumulative effects is crucial for developing effective treatment plans that can better support the holistic development and well-being of these young individuals.

In conclusion, the presence of multiple neurodevelopmental conditions can significantly affect various domains of a young person’s life, with notable differences between males and females. This study provides a critical insight into the intricate nature of these conditions and calls for a more nuanced approach in both research and clinical practice.

Hollingdale J, Woodhouse E, Tibber MS, Simonoff E, Hollocks MJ, Charman T. The cumulative impact of attention deficit hyperactivity disorder, autism and intellectual disability for young people. J Intellect Disabil Res. 2024 Jun 17. doi: 10.1111/jir.13170. Epub ahead of print. PMID: 38887190.

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Norwegian Nationwide Population Study: Single Umbilical Artery Shows Weak Link to ADHD

Counting umbilical cord vessels is standard in prenatal ultrasounds and confirmed at birth. Single umbilical artery (SUA) occurs in about 1 in 200 cases, with roughly 10% associated with anomalies, including central nervous system defects. Isolated SUA (iSUA) means one artery is missing without other structural issues. 

Research on SUA, especially isolated iSUA, and childhood neurodevelopmental disorders (NDD) is limited and inconclusive. iSUA is linked to preterm birth and small-for-gestational age (SGA), both of which are NDD risk factors.  

This Norwegian nationwide population study aimed to assess NDD risk in children with iSUA at birth, the influence of sex, and how preterm birth and SGA mediate this relationship. 

The nation’s universal single-payer health insurance and comprehensive population registries made it possible to analyze all 858,397 single births occurring from 1999 to 2013, with follow-up continuing through 2019. Among these cases, 3,532 involved iSUA. 

After adjusting for confounders such as parental age, education, and maternal health factors, no overall link was found between iSUA and later ADHD diagnosis. However, females with iSUA had about a 40% higher risk of subsequent ADHD compared to those without iSUA, even after adjustment. 

The authors concluded, “The present study indicates that iSUA is weakly associated with ID [intellectual disability] and ADHD, and these associations are influenced by sex. This association is mediated negligibly through preterm birth and SGA. The associations were not clinically significant, and the absence of associations of iSUA with other NDD is reassuring. This finding can be useful in the counseling of expectant parents of fetuses diagnosed with iSUA.” 

 

Large Cohort Study Reports Association Between Eye Disorders and ADHD

Refractive errors, such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism (distorted vision due to irregular curvature of the eye or lens), are common worldwide. These conditions affect 12%, 5%, and 15% of children, and rise significantly in adults to 26.5%, 31%, and 40%. Additionally, strabismus (misalignment of the eyes) and amblyopia (reduced vision in one eye from uneven image formation, often linked to strabismus) occur globally at rates of 2% and 1.4%, respectively. 

Visual impairment can affect children’s concentration in school, and studies suggest a link between eye disorders and ADHD. 

To investigate this relationship, two researchers – one based in the US and the other in Israel –carried out a nationwide retrospective cohort study using electronic medical records of all insured individuals aged 5 to 30 who were part of Maccabi Health Services, Israel’s second largest health maintenance organization, between 2010 and 2022. 

Of over 1.6 million insured members (2010–2020), inclusion/exclusion criteria and propensity score matching for age and sex were applied, along with a one-year wash-out period between the first eye diagnosis and ADHD diagnosis. In total, 221,707 cases were matched with controls without eye disorders at a 1:2 ratio, resulting in a cohort of 665,121 participants.  

Overall, those with any previous eye diagnosis were 40% more likely to have a subsequent ADHD diagnosis. This was slightly higher for females (45%) than for males (35%). It was also slightly higher for children and adolescents (42%) than for adults (37%).  

More specifically: 

  • Myopia (425,000+ participants): 30% higher ADHD rate. 
  • Hyperopia (120,000+) and astigmatism (175,000+): over 50% higher ADHD rate. 
  • Strabismus (13,000+): over 60% higher ADHD rate. 
  • Amblyopia (14,000+): 40% higher ADHD rate. 

The authors concluded that eye disorders are associated with ADHD. They noted these associations were more marked in females and children and adolescents, although, as noted above, those differences were small. They recommended that primary care providers and neurologists consider risk stratification for early screening, and that ophthalmologists refer high-risk patients for ADHD evaluation. 

 

 

February 10, 2026

South Korean Nationwide Population Study: Prenatal Exposure to Acid-suppressive Medications Not Linked to Subsequent ADHD

Acid-suppressive medications, including proton pump inhibitors (PPIs) and histamine-2 (H2) receptor antagonists, are often prescribed during pregnancy to treat heartburn and gastroesophageal reflux disease. 

Research shows changes in the gut microbiome can negatively affect neurodevelopment. Since acid-suppressive medications alter gut microbiota, maternal use during pregnancy may impact offspring’s neurodevelopment. Because PPIs and H2 receptor antagonists readily cross the placental barrier, they could potentially influence fetal neurodevelopment.  

The link between prenatal exposure to acid-suppressive medications and major neuropsychiatric disorders is not well understood. With the use of these medications during pregnancy rising, it is important to assess their impact on children's long-term neurodevelopment. This study examined whether maternal use of acid-suppressive drugs is associated with increased risk of neuropsychiatric disorders in children, using a large, nationwide birth cohort from South Korea. 

South Korea operates a single-payer health insurance system, providing coverage for over 97% of its citizens. The National Health Insurance Service (NHIS) maintains a comprehensive database with sociodemographic details, medical diagnoses, procedures, prescriptions, health examinations, and vital statistics for all insured individuals. 

A Korean research team analyzed data from over three million mother-child pairs (2010–2017) to assess the risks of prenatal exposure to acid-suppressing medications. They applied propensity scoring to adjust for maternal age, number of children, medical history, and outpatient visits before pregnancy, to minimize confounding factors. That narrowed the cohort to just over 800,000 pairs, with half in the exposed group. 

With these adjustments, prenatal exposure to acid-suppressing medications was associated with 14% greater likelihood of being subsequently diagnosed with ADHD. 

Yet, when 151,737 exposed births were compared to the same number of sibling controls, no association was found between prenatal exposure and subsequent ADHD, which suggests unaccounted familial and genetic factors influenced the preceding results. 

The Take-Away:

Evidence of these medications negatively affecting pregnancies is mixed, mostly observational, and generally reassuring when these medications are used appropriately. Untreated GERD and gastritis, however, have known risks and associations with the development of various cancers. With no evidence of an association with ADHD (or for that matter any other neuropsychiatric disorder), there is no current evidence-based reason for expectant mothers to discontinue use of acid-suppressing medications.  

February 6, 2026