Internalizing and externalizing behaviors predict elevated inflammatory markers in childhood

Children with behavior problems, such as internalizing or externalizing disorders, are at increased risk for poorer physical health in adulthood. Inflammation has been posited as a potential biological mediator underlying this association. However, it is unclear how early in development associations between behavior problems and inflammation may be detected, and whether associations are present for both internalizing and externalizing behaviors in pre-pubertal children.

Using data from children in the Avon Longitudinal Study of Parents and Children, we examined associations between behavior problems at age 8 (assessed via the parent-report Strengths and Difficulties Questionnaire) and inflammatory markers assessed at age 10. Inflammatory markers included C-reactive protein (CRP; n=4069) and interleukin-6 (IL-6; n=4061). We further evaluated whether body mass index (BMI) mediated associations, and tested for potential reverse causality by considering whether age 10 inflammation was associated with changes from initial levels to age 12 behavior problems.

After adjusting for relevant covariates, age 8 externalizing behaviors were associated with elevated CRP at age 10, and age 8 internalizing and externalizing behaviors were associated with elevated IL-6 at age 10 (p's<0.05). We found no evidence that observed associations were mediated by BMI or that inflammatory markers at age 10 were associated with increased internalizing or externalizing behavior problems at age 12.

These findings document an association between behavior problems and elevated concentrations of CRP and IL-6 at 10 years. Heightened inflammation in childhood may be a pathway through which early behavior problems increase risk for adult chronic diseases.