Serum cytokines associated with behavior: A cross-sectional study in 5-year-old children

Nearly 10% of 5-year-old children experience social, emotional or behavioral problems and are at increased risk of developing mental disorders later in life. While animal and human studies have demonstrated that cytokines can regulate brain functions, it is unclear whether individual cytokines are associated with specific behavioral dimensions in population-based pediatric samples. Here, we used data and biological samples from 786 mother-child pairs participating to the French national mother-child cohort EDEN. At the age of 5, children were assessed for behavioral difficulties using the Strengths and Difficulties Questionnaire (SDQ) and had their serum collected. Serum samples were analyzed for levels of well-characterized effector or regulatory cytokines. We then used a penalized logistic regression method (Elastic Net), to investigate associations between serum levels of cytokines and each of the five SDQ-assessed behavioral dimensions after adjustment for relevant covariates and confounders, including psychosocial variables. We found that interleukin (IL)-6, IL-7, and IL-15 were associated with increased odds of problems in prosocial behavior, emotions, and peer relationships, respectively. In contrast, eight cytokines were associated with decreased odds of problems in one dimension: IL-8, IL-10, and IL-17A with emotional problems, Tumor Necrosis Factor (TNF)-α with conduct problems, C-C motif chemokine Ligand (CCL)2 with hyperactivity/inattention, C-X-C motif chemokine Ligand (CXCL)10 with peer problems, and CCL3 and IL-16 with abnormal prosocial behavior. Without implying causation, these associations support the notion that cytokines regulate brain functions and behavior and provide a rationale for launching longitudinal studies.