A growing body of studies suggests a link between inflammation and autoimmune diseases on the one hand and ADHD on the other. It has been hypothesized that excessive release of cytokines (small signaling proteins that regulate immune response and inflammation and repair) and keratinocytes (skin cells) under allergic conditions may cause structural and functional changes to the nervous system and brain, which can contribute to psychiatric disorders, including ADHD.

Noting that previous studies have focused primarily on associations between ADHD and respiratory allergies(asthma) and skin allergies, a joint Chinese and American study team set out to see what, if any, association there might be with food allergies.

To this end, they turned to the national health Interview Survey (NHIS), conducted annually by the National Center for Health Statistics at the Centers for Disease Control and Prevention. This survey relies on a very large, nationally representative sample of the U.S. population.

The study encompassed 192,573 youths aged 4 through 17 years old. Of these, 15,376 had an ADHD diagnosis, 8,603 had food allergies, 24,218 had respiratory allergies, and 18,703 had skin allergies.

After adjusting for age, sex, race/ethnicity, education level, family income to poverty ratio, and geographic region, youths with food allergies were found to be over 70% more likely to be diagnosed with ADHD than those without food allergies. After further mutual adjustment for other allergic conditions, they were still well over 40% more likely to be diagnosed with ADHD than their non-allergic peers.

How did that compare with respiratory and skin allergies? In the same study population, making identical adjustments for potential confounders, youths with respiratory allergies were 50% more likely to be diagnosed with ADHD than those without such allergies. Those with skin allergies were 65% more likely to be diagnosed with ADHD. After further mutual adjustment for other allergic conditions, those with respiratory allergies were still over a third more likely to be diagnosed with ADHD, and those with skin allergies were 50% more likely to be diagnosed with ADHD.

The authors concluded, “The current study found a significant and positive association between common allergic conditions, including food allergy, respiratory allergy, skin allergy, and ADHD in children. Although the detailed mechanisms linking food allergy and other allergic conditions to ADHD remain to be understood, physicians should be aware of the increased risk of ADHD as a comorbidity of children with allergic conditions.”

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