Generalized anxiety and C-reactive protein levels: a prospective, longitudinal analysis

Abstract

Generalized anxiety disorder (GAD) is highly co-morbid with depression. Depression is associated with elevated levels of the inflammation marker C-reactive protein (CRP), cross-sectionally and over time. To date, no studies have looked at the association between CRP and GAD. A total of nine waves of data from the prospective population-based Great Smoky Mountains Study (n=1420) were used, covering children in the community aged 9-16, 19 and 21 years old. Structured interviews were used at each assessment to assess GAD symptoms, diagnosis and cumulative episodes. Blood spots were collected and assayed for high-sensitivity CRP levels. GAD was associated with increased levels of CRP in bivariate cross-sectional analyses. These bivariate associations, however, were attenuated after accounting for demographic, substance-use and health-related covariates. In longitudinal models, there was little evidence that CRP predicted later GAD. Associations from GAD to later CRP were attenuated in models adjusted for health-related coavariates and there was evidence that the GAD-CRP association was mediated by body mass index (BMI) and medication use. Similar to depression, GAD was associated with elevated levels of CRP, but the effect of GAD on CRP levels was explained by the effect of GAD on health-related behaviors such as BMI and medication use. This study suggests differences in the association between inflammation and depression and GAD.