Inflammation induces anhedonia, or a loss of enjoyment in things or activities, in women but not in men, researchers found in a study published online in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.
“Our study is the first to show that there are sex differences in neural sensitivity to reward in response to inflammation, which has important implications,” said senior author Naomi Eisenberger, PhD, University of California, Los Angeles. “This may suggest one reason women experience depression at a far greater rate than men, particularly for the kinds of depression that may be inflammatory in nature.”
Researchers randomly assigned 69 women and 46 men to low-dose endotoxin, which increases inflammation, or placebo. Two hours after receiving endotoxin or placebo, participants participated in a game with a monetary reward while undergoing functional magnetic resonance imaging.
Women who received endotoxin showed decreased activity in the brain’s reward region, the ventral striatum, compared with women who received placebo, researchers reported. Men, however, did not.
Among women who received endotoxin, decreases in ventral striatum activity in anticipation of reward were linked with increases in inflammation, the study found.
“This suggests that women with chronic inflammatory disorders may be particularly vulnerable to developing depression through decreases in sensitivity to reward,” said study first author Mona Moieni, PhD, a postdoctoral researcher in the laboratory of Dr. Eisenberger. “Clinicians who treat female patients with inflammatory disorders may want to pay close attention to these patients for possible onset of depressive symptoms.”
Moieni M, Tan KM, Inagaki TK, et al. Sex differences in the relationship between inflammation and reward sensitivity: a randomized controlled trial of endotoxin. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. 2019 April 3;[Epub ahead of print].