Genetic and environmental influences to low back pain and symptoms of depression and anxiety: A population-based twin study

Background: People suffering from chronic pain are more likely to experience symptoms of depression and anxiety. However, the mechanisms underlying this relationship remain largely unknown. In light of the moderate to large effects of genetic factors on chronic pain and depression and anxiety, we aimed to estimate the relative contribution of genetic and environmental factors to the relationship between these traits. Methods: Using data from 2139 participants in the Murcia Twin Registry, we employed a bivariate analysis and structural equation modeling to estimate the relative influences of genetics and the environment on the covariation between low back pain and symptoms of depression and anxiety. Results: We have obtained heritability estimates of 0.26 (95% Confidence Interval (CI) 0.11, 0.41) for chronic low back pain and 0.45 (95% CI 0.29, 0.50) for symptoms of depression and anxiety. The phenotypic, genetic, and unique environment correlations in the bivariate analytical model were, respectively, r(ph) = 0.26 (95% CI 0.19, 0.33); r(G) = 0.47 (95% CI 0.42, 0.70); r(E) = 0.14 (95% CI -0.04, 0.25). The percentage of covariance between low back pain and symptoms of depression and anxiety attributable to additive genetic factors was 63.6%, and to unique environment 36.4%. Conclusions: Our findings confirm the relationship between low back pain and symptoms of depression and anxiety in a non-clinical sample. Shared genetic factors affect significantly the covariation between these conditions, supporting the role of common biological and physiological pathways.