3. Results
The characteristics of the study population are presented in Table 1. The individuals in the MDD group more often lived alone, smoked, and used antidepressant medication. They also showed higher scores on all the depression scales used in the present study, i.e. HAM-D-21, HAM-D-29, ADS, and BDI. The levels of IL-5, IL-13 and IFN-γ did not significantly differ between the groups in the crude analysis. Moreover, scatterplots were formed to visualize the relationships between IL-5 (Figure 1), IL-13 (Figure 2) and IFN-γ (Figure 3) and the BDI scores from the 2005 questionnaire.
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Figure 1.
Scatterplot of IL-5 levels in relation to BDI scores from the 2005 questionnaire.
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Figure 2.
Scatterplot of IL-13 levels in relation to BDI scores from the 2005 questionnaire.
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Figure 3.
Scatterplot of IFN-γ levels in relation to BDI scores from the 2005 questionnaire.
In the multivariate models (Table 2) controlling for the effects of potential confounders on the associations between depression and the examined cytokines, each 1-unit increase in the serum IL-5 levels increased the likelihood of belonging to the MDD group by 76% (OR 1.76, 95% CI 1.03–2.99, p = 0.038) in Model 1 adjusted for age, gender, marital status, daily smoking, and alcohol use. The observations remained essentially similar in the other models further adjusted for the use of antidepressants (Model 2: OR 2.06, 95% CI 1.16–3.63, p = 0.013), the use of NSAIDS (Model 3: OR 1.89, 95% CI 1.10–3.27, p = 0.022) and a diagnosis of asthma (Model 4: OR 1.83, 95% CI 1.07–3.14, p = 0.028). No such associations were observed for IL-13 or IFN-γ (Table 2).