Molecular foundation of anxiety disorders

Genetic epidemiology has assembled convincing evidence that anxiety and related disorders are influenced by genetic factors and that the genetic component is highly complex, polygenic, and epistatic. Although several genes which may contribute to the genetic variance of anxiety-related traits or modify the phenotypic expression of pathologic anxiety are currently under investigation, molecular genetics has so far failed to identify a genomic variation that can consistently contribute susceptibility of anxiety disorders. Investigation of gene-gene and gene-environment interactions in humans and nonhuman primates as well as gene inactivation studies in mice further intensify the identification of genes that are essential for development and adult plasticity of the brain related to complex anxiety responses. Because the modes of inheritance of anxiety disorders are complex, it has been concluded that multiple genes of small effect, in interaction with each other and with nongenetic neurodevelopmental events, produce vulnerability to the disorder. Future research directions will take advantage of the completion of the sequencing the human and mouse genome coinciding with the revolution in bioinformatics. More than 1.4 million single nucleotide polymorphisms (SNPs) in the human genome have been identified. This collection should allow the initiation of genome-wide linkage disequilibrium mapping of the genes influencing anxiety in the human population. Integration of these emerging tools and technologies for genetic analysis will provide the groundwork for an advanced stage of gene identification and functional studies in anxiety and related disorders.