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January 16, 2024
Infants begin to transition from breast or formula milk to solid food at about six months of age, as they gradually develop interest in food and the ability to chew.
The American Academy of Pediatrics recommends breastfeeding for the first six months. The European Society of Pediatric Gastroenterology Hepatology and Nutrition recommends initiation of supplementary food around that time. The World Health Organization (WHO) has set a 2025 goal of getting most mothers worldwide to breastfeed exclusively through the first six months of infancy.
Noting that “inconsistent findings have been reported in previous national survey-based studies,” a South Korean study team conducted a nationwide population study to explore the relationship between breastfeeding and subsequent rates of ADHD.
South Korea has a mandatory single-payer national health insurance system – the National Health Insurance Service (NHIS) – that covers virtually the entire population. Detailed and consistent NHIS records facilitate nationwide population studies.
One NHIS program is the National Health Screening Program for Infants and Children (NHSPIC), which includes periodic examinations by trained pediatricians up to six years of age.
Using these national records, the team identified a cohort of over 1.1 million infants. These same records show that a little over a third (36%) received nothing but formula milk feeding during their first six months. About a fifth (21%) received a mix of formula and breast feeding. Almost a half (43%) were exclusively breastfed.
ADHD diagnoses were made by physicians during hospital visits.
The team adjusted for a series of confounders that were found to influence outcomes: sex, year of examination, residence, socioeconomic status, preterm birth, birth weight, and body measurements (weight, microcephaly) at examination (4–6 months of age).
With these adjustments, partial breastfeeding was associated with a small but significant (9%) reduction in the odds of infants later being diagnosed with ADHD, relative to infants receiving only formula milk feeding.
Exclusive breastfeeding was associated with a much larger 23% reduction in the odds of infants later being diagnosed with ADHD, relative to exclusive formula feeding.
What’s especially noteworthy is the dose-response pattern that suggests that breastfeeding may have a protective effect.
A separate analysis comparing infants who began transitioning to supplementary solid food before versus after six months found absolutely no difference in the odds of subsequently being diagnosed with ADHD.
A similar pattern emerged for autism spectrum disorder on all counts, again reflecting a dose-response pattern, pointing to what may be a broader beneficial effect of breastfeeding for healthy neurologic development.
The team concluded, “The risk of ADHD and ASD [autism spectrum disorder] considerably decreased with breastfeeding, and this tendency was more prominent in children who received EBF [exclusive breastfeeding] than in those who received PBF [partial breastfeeding]. Our study strengthens and supports the idea that breastfeeding is beneficial in preventing NDDs [neurodevelopmental disorders] in children. We suggest that breastfeeding be encouraged and recommended to promote good neurodevelopmental outcomes.”
Jong Ho Cha, Yongil Cho, Jin-Hwa Moon, Juncheol Lee, Jae Yoon Na, and Yong Joo Kim, “Feeding practice during infancy is associated with attention-deficit/ hyperactivity disorder and autism spectrum disorder: a population-based study in South Korea,” European Journal of Pediatrics (2023), https://doi.org/10.1007/s00431-023-05022-z.
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:
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.
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.
For years, a persistent concern has shadowed the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD): Does the medication eventually stop working? Patients often report that their symptoms seem to return despite consistent use, leading to "dose escalation" or "medication holidays." A new systematic review from Sam Cortese’s team published in CNS Drugs finally puts these concerns to the test by synthesizing decades of empirical research.
Before diving into the findings, you must understand two often-confused phenomena:
The review analyzed 17 studies covering over 10,000 individuals, and the results provide a much-needed reality check for the clinical community.
The researchers found preliminary evidence that acute tolerance (tachyphylaxis) can occur within a 24-hour window.
The most important finding is that tolerance does not commonly develop to the therapeutic effects of ADHD medication in the long term. In one landmark study following children for up to 10 years, only 2.7% of participants lost their response to methylphenidate without a clear external explanation. Doses, when adjusted for natural body growth, remained remarkably stable over years of treatment.
Consistent with the lack of therapeutic tolerance, the body does not become tolerant to the physical side effects of stimulants. Increases in heart rate and blood pressure typically persist for as long as the medication is taken. This underscores why clinicians must continue monitoring cardiovascular health throughout the entire duration of treatment.
If it’s Not Tolerance, What Is It?
If "tolerance" isn't real, why do some patients feel their medication is failing? The review suggests clinicians look at these alternative explanations:
Why This Matters
These results provide clinicians the confidence to tell patients that their medication is unlikely to "wear out" permanently. Rather than immediately increasing a dose when symptoms flare, the first step should be a "clinical deep dive" into the patient's lifestyle, stress levels, and adherence.
For researchers, the review highlights a major gap: most existing studies are small, dated, or of low quality. There is a dire need for robust, longitudinal studies that track both the brain's response and the patient's environment over several years.
For people with ADHD, while your body might get "used to" the initial "buzz" of a stimulant within hours, its ability to help you focus and manage your life remains remarkably durable over the years.
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