Sex differences in depressive and socioemotional responses to an inflammatory challenge: implications for sex differences in depression.
Level 2 - randomized trial
Individual double-blind, placebo-controlled randomized trial
PubMed 25598426 · doi:10.1038/npp.2015.17
What was done
In a double-blind, placebo-controlled randomized clinical trial, 115 healthy participants (69 female) were randomly assigned to receive a single infusion of low-dose endotoxin (derived from Escherichia coli; 0.8 ng/kg of body weight) or placebo (same volume of 0.9% saline). Tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), depressed mood, and feelings of social disconnection were assessed hourly.
What was found
Endotoxin (vs placebo) led to increases in proinflammatory cytokines (TNF-α, IL-6), depressed mood, and feelings of social disconnection. Females exposed to endotoxin showed greater increases in depressed mood and feelings of social disconnection compared to males. Increases in TNF-α and IL-6 correlated with increases in social disconnection for females but not for males. The abstract does not report specific numerical values, effect sizes, or p-values.
Why it matters
This trial demonstrates experimental human evidence that females have heightened socioemotional sensitivity to acute inflammation, providing a potential biological mechanism for the higher incidence of depression in women.
Limits
The study tested acute endotoxin challenge in healthy individuals rather than chronic inflammation in clinical depression. Specific numerical results, effect sizes, and subgroup sample sizes per treatment arm are not reported in the abstract.
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