Cytokine Genes TNF, IL1A, IL1B, IL6, IL1RN and IL10, and childhood-onset mood disorders

Background/aims: Inflammatory cytokines induce a behavioral syndrome, known as sickness behavior, that strongly resembles symptoms typically seen in depression. This resemblance has led to the theory that an imbalance of inflammatory cytokine activity may be a contributing factor in depressive disorders. Support for this is found in multiple lines of evidence, such as the effects of cytokines on the activities of the hypothalamic-pituitary-adrenal axis, serotonin and brain-derived neurotrophic factor, and hippocampal function, all of which are implicated in the etiology of depression. In addition, associations between inflammatory activity and depressive symptomology have been documented in a number of studies, and the depressogenic effects of cytokine therapy are well known. Accordingly, given that depression has a substantial genetic basis, genes involved in the regulation of inflammatory cytokine activity are strong candidates for involvement in genetic susceptibility to depressive disorders. Here, we have tested 6 key genes of this type, TNF, IL1A, IL1B, IL6, IL1RN and IL10, as candidates for involvement in childhood-onset mood disorders.

Methods: In this study of 384 families, each ascertained through a child with depression diagnosed before the age of 15 years, 11 polymorphisms of known or likely functional significance (coding and regulatory variants) were analyzed.

Results: Testing for biased transmission of alleles from parents to their affected offspring, we found no evidence for an association between childhood-onset mood disorders and any of the polymorphisms, either individually or as haplotypes.

Conclusion: The present study does not support the involvement of the TNF, IL1A, IL1B, IL6, IL1RN and IL10 variants as major genetic risk factors contributing to early-onset mood disorders.