Plasma levels of interleukin-6 and selective serotonin reuptake inhibitor response in patients with major depressive disorder

Objective We investigated the plasma levels of interleukin (IL)‐6 and 5‐HTT polymorphisms in patients with major depressive disorder (MDD). This is the first report, to our knowledge, of an investigation into the association between 5‐HTT gene polymorphism, plasma IL‐6 levels, and responses to selective serotonin reuptake inhibitors (SSRIs) in Japanese patients with MDD. Method One‐hundred and eighteen patients (51 male, 67 female) who met the DSM‐IV criteria for MDD were enrolled. Their ages ranged from 24 to 78 (mean ± SD = 44 ± 12) years. The patients were treated with SSRIs (paroxetine in 66 cases, sertraline in 42 cases) for 8 weeks. Results The plasma levels of IL‐6 were significantly higher in the SSRI responders than in the nonresponders (p = 0.0328), and the changes in plasma IL‐6 levels correlated significantly with the changes in severity of depressive state (p = .0.007). No difference was found in baseline and the changes in plasma IL‐6 levels between the patients with a 5‐HTT gene (5‐HTTLPR) L‐carrier and those with S/S. Conclusion These results suggest that the plasma levels of IL‐6 reflect the severity of MDD and that plasma IL‐6 levels might be another biological‐state marker for the depressive state. In addition, the 5‐HTTLPR polymorphism might be independent of plasma IL‐6 levels. Copyright © 2013 John Wiley & Sons, Ltd.