How are Allergies Linked to ADHD?

Allergies and asthma found to increase the risk of ADHD in children

(RxWiki News) There has been some evidence that children with ADHD may be more likely to have asthma or allergies as well. New research looked to examine the issue.A recent study examined the relationship between a medical history of various allergies and the diagnosis of ADHD (attention-deficit/hyperactivity disorder) in children.

The findings showed that a history of asthma, impetigo, intolerance to cow's milk and use of prescription medications were linked to an increased risk of ADHD in boys ages 4 to 14.

"Discuss your child's health history with a doctor."

Lead author Eelko Hak, PhD, professor and researcher from the Department of Epidemiology, University Medical Center Groningen at the University of Groningen and colleagues tried to determine whether or not children with a medical history of ADHD were more likely to have a history of atopic disorders, skin infections and prescription medicines.

An atopic disorder is a non-contagious, typically genetic condition where the body has an intense allergic reaction when exposed to a certain trigger, such as pollen, dust or certain chemicals.

The atopic disorders included in this study were atopic dermatitis (inflamed, itchy skin), allergic rhinitis (hay fever), food allergies, intolerance to cow's milk and general, nonspecific allergies. Asthma is also an atopic disorder, and the authors considered any instance of allergic asthma, detergent asthma (reaction to chemical in laundry detergent), exercise-induced asthma and general nonspecific asthma.

The authors explained that there has been a growing number of studies over the past decade on the connection between ADHD and allergies in children. This study focused only on boys because boys are more likely to be diagnosed with ADHD.

The researchers selected a group of 884 boys between the ages of 4 to 14, all of whom had been first diagnosed with ADHD between the years of 1996 and 2006. All of them had been treated at least once with methylphenidate (brand names Concerta, Ritalin) — the most popular ADHD medicine in the UK — during their first 12 months after being diagnosed.

The researchers then selected a group of 3,536 boys who did not have ADHD as the comparison group. 

The researchers then examined the records for cases of atopic disorders, impetigo and the use of prescribed medicines used to treat these allergies and infections.

Low birth weight and instances of preterm birth were also considered because asthma and ADHD have been associated with both.

The researchers first conducted an analysis to see what factors the ADHD and the non-ADHD group had in common, and how often the commonality occurred. Then the researchers analyzed all other factors against each other, including any differences between the older group of children and the younger group.

The findings showed that ADHD was associated with asthma, cow's milk intolerance, impetigo and the use of prescription medications to treat atopic disorders and skin infections.

A total of 34 percent of the ADHD group was affected by asthma compared to 25 percent of the non-ADHD group.

The researchers also found that 1.5 percent of the ADHD group had intolerance to cow's milk, compared to 0.7 percent of the non-ADHD group. A total of 21 percent of the ADHD group was affected by impetigo, compared to 15 percent of the non-ADHD group.

Overall, 44 percent of the ADHD group had atopic disorders and 34 percent of the non-ADHD group was found to have atopic disorders.

The authors stated that these findings are in line with previous evidence that asthma and allergies increase the risk for ADHD in children.

This study was published in the August edition of the Annals of Allergy, Asthma and Immunology.

Review Date: 
August 23, 2013