Table 1.
Summary of epidemiological link between allergy and ADHD.
| Title of article | Country | Study design | Sample size | Age range in years | Allergic conditions | Outcome |
|---|---|---|---|---|---|---|
| Infant atopic eczema and subsequent attention-deficit hyperactivity disorder – A prospective birth cohort study (21) | Germany | Prospective birth cohort study | 770 | Birth to 11 | •Atopic eczema (AE) | •Parental reported AE in early life up to 4 years was significantly associated with both early and late ADHD (RR: 1.92, 95% CI: 1.03–3.57) •Doctor diagnosed AE in first 4 years of life was significantly associated with early development of ADHD in first 8 years of life (RR: 2.58, 95% CI: 1.11–5.99) |
| Association between childhood asthma and ADHD symptoms in adolescence—A prospective population-based twin study (22) | Sweden | Prospective population-based twin study | 1,812 | First timepoint: 8–9 Second timepoint: 13–14 |
•Asthma | •Asthma at 8–9 years was significantly linked with elevated risks of 4 (OR: 2.77, 95% CI: 1.23–6.26), 5 (OR: 3.62, 95% CI: 1.04–12.57), or 6 (OR: 8.36, 95% CI: 1.52–45.81) symptoms of inattention at 13–14 years •Children with asthma at 8–9 years exhibited more than double the odds of having 3 hyperactivity–impulsivity symptoms at 13–14 years (OR: 2.50, 95% CI: 1.46–4.28) |
| Longitudinal association between early atopic dermatitis and subsequent attention-deficit or autistic disorder (23) | Taiwan | Population-based case–control study | 18,473 AD, 18,473 controls | 1 month−3 years | •AD •Asthma •AR •Allergic conjunctivitis |
•Children with AD had significantly earlier age of diagnosis for ADHD compared with controls (p < 0.001) •AD in children was significantly associated with elevated risks of development of ADHD (HR: 2.92, 95% CI: 2.48–3.45) and ASD (HR: 8.90, 95% CI: 4.98–15.92) •Comorbid asthma, AR, and allergic conjunctivitis further increased the risk of ADHD (HR: 4.67, 95% CI: 3.81–5.43) and ASD (HR: 16.25, 95% CI: 8.63–30.60) |
| Association between atopic dermatitis and attention deficit hyperactivity disorder in U.S. children and adults (24) | United States | Cross-sectional population-based surveys | 354,416 children 34,613 adults | Children: 2–17 Adults: 18 and above |
•AD •Asthma •Hay fever |
•AD in children was significantly linked with elevated risks of ADHD (p < 0.05) after adjustment for health-care utilization, sociodemographic data, and comorbid allergic disease •AD in adults was significantly linked with elevated risks of ADHD (p < 0.05) after adjustment for health-care utilization, sociodemographic data, and comorbid allergic disease •All severity levels of ADHD including mild, moderate, and severe were significantly linked with elevated risks of AD (p < 0.05) |
| Association between allergic diseases, allergic sensitization and attention-deficit/hyperactivity disorder in children: A large-scale, population-based study (25) | Taiwan | Population-based cross-sectional survey | 2,772 | 3–6 | •AD •Asthma •Allergic rhinitis •Allergic conjunctivitis •Food allergy |
•AD comprising allergic sensitization was significantly linked with ADHD (p < 0.05) after adjustment for age, birth weight, sex, maternal history of allergy, maternal education, and period of breastfeeding •Asthma comprising allergic sensitization was significantly linked with ADHD (p < 0.05) after adjustment for age, birth weight, sex, maternal history of allergy, maternal education, and period of breastfeeding •Sensitization to mite allergen was significantly associated with ADHD (p < 0.05) |
| Association between atopic diseases and attention-deficit hyperactivity disorder in childhood: A population-based case-control study (26) | Taiwan | Population-based case–control study | 4,692 ADHD, 18,768 controls | Up to 18 | •AD •Asthma •Allergic rhinitis •Allergic conjunctivitis |
•AD, AR, asthma, and allergic conjunctivitis were all significantly linked with ADHD independently (p < 0.001) •Increasing number of allergic diseases was significantly associated with increasing risk of ADHD after adjustment for age, sex, and urbanization (p < 0.001) |
| The associations between ADHD and asthma in Korean children (27) | Korea | Longitudinal study | 549 ADHD, 3,564 controls | 7–8 | •AD •Asthma •AR •Allergic conjunctivitis •Food allergy •Drug allergy |
•Significantly higher proportion of children in the ADHD group had a history of asthma (p < 0.001) and AR (p < 0.001) compared with those in the control group •Compared with controls, a significantly higher proportion of children in the ADHD group had received treatment for asthma in the past 12 months (p = 0.031) •Compared with controls, a significantly higher proportion of children in the ADHD group had received treatment for AR in the past 12 months (p = 0.007) |
| Early food allergy and respiratory allergy symptoms and attention-deficit/hyperactivity disorder in Chinese children: A cross-sectional study (28) | China | Cross-sectional study | 22,018 | Mean age: 8.8 ± 1.8 | •Food allergy •AR •Asthma |
•Food allergy was significantly associated with elevated risks of ADHD (p < 0.001) •Food allergy with concurrent AR and/or asthma further increased the risk of ADHD (p < 0.001) |
AE, atopic eczema; AD, atopic dermatitis; AR, allergic rhinitis; ADHD, attention-deficit hyperactivity disorder; RR, relative risk; OR, odds ratio; HR, hazard ratio.