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Figure 1. Interleukin (IL)-6 (A) and tumor necrosis factor (TNF)- (B) plots showing the predicted cytokine response by n-6:n-3 ratio separately for different Center for Epidemiological Studies Depression Scale (CES-D) depressive symptom levels. Although the analyses used continuous variables, predicted cytokine values are plotted for the midpoint of each depressive symptom quartile (2,4,9,18) to illustrate the effect of depression on the cytokine n-6:n-3 ratio relationship. The predicted values for IL-6 and TNF- are nonlinear because the model was on the log scale; then, the predicted values were transformed back to the original scale. In the IL-6 soluble receptor (sIL-6r) model (C), the n-6:n-3 ratio main effect was significant, and the ratio did not differ significantly by depression. Therefore, only one response curve is on the plot, at the mean depression level of 7.4. Responses at other depression levels would yield parallel curves.
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