Association of childhood attention-deficit/hyperactivity disorder with atopic diseases and skin infections? A matched case-control study using the General Practice Research Database.

BACKGROUND: Data to support the hypothesis of a relationship between attention-deficit/hyperactivity disorder (ADHD) and allergies are conflicting.
OBJECTIVE: To assess whether children with ADHD are more likely to have a history of atopic disorders, skin infections, and medical prescriptions than children without ADHD.
METHODS: We conducted a nested case-control study among boys using the UK General Practice Research Database (GPRD). Cases were defined as children with first-time diagnosis of ADHD who were treated with methylphenidate. Four controls who had neither ADHD nor ADHD drug prescriptions in their medical records were matched to each case on age and general practice.
RESULTS: We identified 884 boys with a first-time diagnosis of drug-treated ADHD and 3,536 controls. The independent odds ratios adjusted for age and presence of low birth weight or preterm delivery were 1.4 (95% confidence interval [CI], 1.2-1.7; P < .001) for a medical history of asthma, 1.5 (95% CI, 1.3-1.9; P < .001) for impetigo, and 1.5 (95% CI, 1.3-1.7; P < .001) for any antihistamine drug prescriptions. Other exposures that were more common in cases than controls, though not independently, were cow's milk intolerance and any prescription from the drug categories antiasthmatics, respiratory corticosteroids, topical steroids, antibacterials, or antifungals.
CONCLUSION: Despite possible limitations inherent to observational studies, this study lends support to the emerging evidence that childhood ADHD is associated with atopic diseases and impetigo. Further interdisciplinary research is needed to understand the underlying mechanisms and to evaluate targeted preventive, diagnostic, and therapeutic interventions.