Chronic widespread pain: clinical comorbidities and psychological correlates.

Recent studies have provided consistent evidence for a genetic influence on chronic widespread pain (CWP). The aim of this study was to investigate (1) the etiological structure underlying CWP by examining the covariation between CWP and psychological comorbidities and psychoaffective correlates and (2) the decomposition of the covariation into genetic and environmental components. A total of 3266 female twins (mean age 56.6 years) were subject to multivariate analyses. Using validated questionnaires to classify twins as having CWP, the prevalence of CWP was 20.8%. In the multivariate analysis, the most suitable model was the common pathway model. This model revealed 2 underlying latent variables, one common to anxiety, emotional intelligence, and emotional instability (f1) and the other common to depression and CWP (f2), the latter being highly heritable (86%). Both latent variables (f1 and f2) shared an additive genetic and a nonshared environmental factor. In addition, a second additive genetic factor loading only on f2 was found. This study reveals the structure of genetic and environmental influences of CWP and its psychoaffective correlates. The results show that the clustering of CWP and depression is due to a common, highly heritable, underlying latent trait. In addition, we found evidence that CWP, anxiety, emotional instability, and emotional intelligence are influenced by different underlying latent traits sharing the same genetic and nonshared environmental factors. This is the first study to reveal the structure and relative importance of genetic and environmental influences on complex etiological mechanisms of CWP and its correlates.