Psychosocial distress and inflammation: Which way does causality flow?

OBJECTIVES: This study queried causal direction in linkages of inflammation with psychosocial distress.

METHODS: Data were from the 2005-2006 and 2010-2011 waves of the U.S. National Social Life, Health, and Aging Project. Inflammation was indicated by C-reactive protein, and distress by depression, anxiety, as well as stress. Autoregressive cross-lagged panel models were used to examine causal direction.

RESULTS: Rather than being an outcome of psychosocial distress, inflammation was a predictor of it. Linkages were gender differentiated, with inflammation seeming to induce depression among men but stress among women.

DISCUSSION: Contrary to previous literature, inflammation may not be a mechanism through which psychosocial distress gets "under the skin" to cause cardiovascular and metabolic issues. Rather, it may be a node through which social pathologies and life events influence both mental health and physiological problems.