Genetic and environmental contributions to the relationship between education and anxiety disorders - a twin study.

OBJECTIVE To examine the negative statistical relationship between educational level and risk of anxiety disorders, and to estimate to what extent this relationship may be explained by genes or environmental factors influencing both phenotypes. METHOD Registry data on educational level for 3339 young adult Norwegian twin pairs and diagnostic data on anxiety disorders for 1385 of these pairs were analysed, specifying structural equations models using MX software. RESULTS In the best-fitting model, genes accounted for 59% of the variance in education. 18% of the variance was due to environmental factors shared by co-twins, and the remaining 23% due to non-shared environment; 46% of the variance in liability to anxiety disorders was genetic, the remaining variance was due to non-shared environment. A phenotypic polychoric correlation of -0.30 between educational level and 'any anxiety disorder' was estimated to be primarily (83% in the best-fitting model) caused by genes common to the two traits. CONCLUSION The relationship between low education and risk of anxiety disorders appears to be primarily determined by genetic effect common to educational level and anxiety disorders.