Circulating cytokine concentrations are not associated with major depressive disorder in a community-based cohort

Objective: The objective was to test the hypotheses that cytokine levels are elevated in community-residing persons at high risk for obstructive sleep apnea with major depressive disorder (MDD) compared to nondepressive persons and that cytokine levels show stronger correlations with somatic than psychological symptoms of depression. Method: A case-control study within the cross-sectional Akershus Sleep Apnea Project was performed. Two controls matched for age, gender, metabolic syndrome and obstructive sleep apnea were drawn for each case of MDD. Results: Group comparisons revealed no significant difference in the levels of 17 cytokines [interleukin-1β, -2,-4, -5, -6, -7, -8, -10, -12(p70), -13 and -17; tumor necrosis factor-α; interferon-γ; granulocyte colony-stimulating factor; granulocyte-monocyte colony-stimulating factor; macrophage chemoattractant protein-1 and monocyte inhibitory protein-1β] between persons with (n=34) and without MDD (n=68). There was no association between cytokines levels and MDD in multivariate regression analyses. The concentration of interleukin-4 was significantly more positively correlated with psychological than somatic symptoms (r=0.046 vs. -0.143, respectively, P=0.024), while no different correlations were observed for other cytokines. Conclusion: The cytokine levels were not elevated in MDD, and cytokine levels were not more strongly associated with somatic than psychological symptoms of depression. The depression-specific effect on inflammation may be weak in community-based samples with prevalent somatic comorbidity.