Trajectories of internalising and externalising symptoms and inflammation in the general child population.

BACKGROUND: Elevations in inflammatory marker levels have been shown to precede internalising and externalising problems in the general child population. One study has found the reverse, that elevations in inflammatory marker levels in childhood follow internalising and externalising problems. However, the authors did not explore the role of the course of these problems in childhood or adjust for a number of potential confounders including psychosocial stressors and prenatal and perinatal exposures. AIMS: To investigate the association in childhood between the growth of internalising and externalising symptoms and levels of inflammatory markers, while accounting for potential confounders. METHODS: Using data from the Avon Longitudinal Study of Parents and Children, we tested the association between the trajectories of internalising (emotional and social) and externalising (hyperactivity and conduct) problems, at ages 4, 6, 8 and 9 years, and levels of C-reactive protein (CRP) and interleukin 6 (IL-6) at age 9 years. We analysed data (n = 4525) using latent growth curve modelling and linear regression. RESULTS: Children who had increasing levels of internalising symptoms over childhood were more likely to have higher levels of CRP and IL-6 at 9 years of age, even after adjustment for confounders. A one-unit increase in the rate of annual change of internalising symptoms was related to an increase of 12% and 8% in the level of CRP and IL-6, respectively. However, there was no evidence for an association between externalising symptoms and either inflammatory marker. CONCLUSIONS: This study is the first step towards identifying a robust pathway, via increases in emotional and social difficulties, to elevated inflammation in healthy children. This association, if causal, suggests that effective interventions for children experiencing chronic emotional and social difficulties could also have physical health benefits.