Interleukin-1beta (IL-1beta) gene and increased risk for the depressive symptom-dimension in schizophrenia spectrum disorders.

Abstract

Interleukin-1beta (IL-1beta), as well as other cytokines, has been classically implicated in the pathophysiology of major psychiatric disorders such as schizophrenia and major depression, and recent studies have implicated the IL-1beta gene and schizophrenia. Nevertheless, new approaches to this complex phenotype are necessary to clarify the risk conferred by this gene, either to the disorder or to its clinical manifestations. The aim of the present study was to explore the effect of a genetic polymorphism of the promoter region of the IL-1beta gene, in schizophrenia defined with: (i) a categorical diagnosis and (ii) a multidimensional symptom approach. We studied 356 individuals from 89 nuclear families consisting of one affected individual and the unaffected father, mother, and sib, in a family-based association study design. We find a trend for biased transmission of allele 2 from heterozygous parents to affected offspring, categorically defined (P = 0.07). This tendency was not observed in the healthy offspring. Using a multidimensional symptom approach to the diagnosis, the association was confirmed in psychotic patients showing the depressive symptom-dimension (P = 0.02).