Inflammation appears to increase anhedonia — a loss of enjoyment in things or activities — in women, but not in men, according to a new study published in the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.
Reduced activity in the brain’s reward center is the signature of anhedonia, a core feature of depression. Women are two-to-three times more likely to be diagnosed with depression, and the new findings highlight a key difference in men and women that could contribute to the uneven rates of the disorder.
“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, Ph.D., 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.”
In the study, healthy men and women received a substance to increase inflammation. The research team measured activity in the reward region of the brain, the ventral striatum, as the participants played a game where they could win a monetary reward.
The findings show that women with greater inflammatory responses exhibited less brain response in anticipation of potential rewards, but the association was not present in men.
“This suggests that women with chronic inflammatory disorders may be particularly vulnerable to developing depression through decreases in sensitivity to reward,” said first author Mona Moieni, Ph.D., a postdoctoral researcher in the laboratory of Eisenberger.
“Clinicians who treat female patients with inflammatory disorders may want to pay close attention to these patients for possible onset of depressive symptoms.”
Cameron Carter, M.D., editor of Biological Psychiatry: Cognitive Neuroscience and Neuroimaging said “This study highlights the important gender differences that exist in the human brain and suggests a mechanism that might help explain the greater prevalence of depression in women compared to men.”
Researchers suggest since the increased inflammation had no effect on how men’s brains responded to reward, inflammation-induced anhedonia may be an important contributor to the higher rates of depression in women.