BACKGROUND: Allergic disease and common mental disorders frequently co-occur. However, little is known about the longitudinal impact of childhood allergy on the subsequent risk of developing anxiety or depression, and the possible biological mechanisms for this. METHODS: We performed longitudinal analyses of data from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. The baseline sample comprised n = 5256 children with allergy data available at age 7yrs. We used multivariable regression to test associations between childhood allergy at age 7yrs and: a) four inflammatory markers at age 9yrs
b) depression and anxiety measures between ages 10-24yrs. Allergy measures included biological markers (total serum immunoglobulin E (tIgE), number of positive skin prick tests (SPTs)), and presence of eczema, asthma and/or food allergy (mother reported). Inflammatory markers were interleukin-6 (IL-6), C-reactive protein (CRP), IL-4 and IL-13. We used structural equation modelling to test whether inflammatory markers mediated the association between tIgE and depression/anxiety. RESULTS: tIgE and having ≥ 1 positive SPT at age 7 were associated with IL-6 levels at age 9 (adjusted β = 0.09
95 % CI 0.06-0.13
p <
0.001 and adjusted β = 0.06
95 % CI 0.03-0.09
p <
0.001 respectively), but not with CRP, IL-4 or IL13 levels. We found no strong evidence of an association between childhood allergy and subsequent depression/anxiety during adolescence and early adulthood. This finding was consistent across biological and mother-reported allergy measures. CONCLUSIONS: Biological markers of childhood allergy are associated with IL-6, a key inflammatory cytokine. However, childhood allergy may not have a large long-term effect on subsequent depression/anxiety.