The role of inflammation in acute psychosocial stress-induced modulation of reward processing in healthy female adults.

BACKGROUND: Anhedonia, or loss of interest and pleasure, is a pernicious symptom of depression that involves deficits in reward processing. Stress-induced inflammation is a plausible biopsychosocial mechanism of reward deficits, but little is known whether stress-induced inflammation alters reward behavior. The present study (a secondary analysis of a completed randomized controlled trial) tested whether acute stress activated a key pro-inflammatory transcription control pathway, NF-κB, and whether this activation was associated with acute stress-induced modulation of reward processing. METHODS: Healthy female adults (age 18-25) were randomized to undergo an acute psychosocial stressor (Trier Social Stress Test; n = 36) or a no-stress active control (n = 16). The Probabilistic Reward Task (PRT) (n = 30 stress; n = 12 control) was administered at baseline and at 90 min post-stress, coinciding with the peak of the stress-induced inflammatory response. Genome-wide expression profiling and bioinformatics analyses of NF-kB transcription factor activity were used to assess pro-inflammatory gene regulation. RESULTS: Relative to the control condition, stress increased bioinformatic measures of NF-κB transcription factor activity (p = .01) and increased reward response bias scores on the PRT (p = .03). Within the stress condition, greater NF-κB activity was associated with greater increases in PRT scores (p = .01), whereas in the control condition greater NF-κB activity was associated with decreases in PRT scores (p = .002). CONCLUSIONS: Acute stress increases inflammatory signaling, and this effect is associated with increased reward processing. This demonstrates the reward system to be highly sensitive to inflammatory signaling, including the relatively mild alterations that occur following a single episode of acute psychosocial stress