Inflammation and Specific Symptoms of Depression

Abstract

Elevated levels of inflammatory markers, such as C-reactive protein, are well-documented in people with depression. 1,2 Rai-son and Miller 3 suggested that this association may, in fact, be symptom-specific. Higher levels of inflammation are particu-larly likely to underlie depression symptoms that character-ize sickness behavior, including fatigue, reduced appetite, with-drawal, and inhibited motivation. From an evolutionary perspective, such symptoms have the beneficial effect of pre-serving energy resources for use in fighting infection and pro-moting healing processes. 4,5 Here, we tested the hypothesis that the association between C-reactive protein and depres-sion is symptom-specific. Methods | Data were collected from 3 cross-sectional studies: the US National Health and Nutrition Surveys of 2005-2006 (n = 4593), 2007-2008 (n = 5151), and 2009-2010 (n = 5327) that underwent National Center for Health Statistics institutional re-search ethics review board approval. 6 Written informed consent was obtained from all participants. We included all 15 071 par-ticipants with relevant data (mean age, 47.5 years; 50.1% female) whether or not they had specific symptoms of depression. C-reactive protein was measured using standard procedures (me-dian, 2 mg/L; interquartile range, 0.8-4.7 mg/L; to convert to nanomoles per liter, multiply by 9.524). 6 C-reactive protein