Pro-inflammatory cytokines are elevated in adolescent females with emotional disorders not treated with SSRIs

Background: Adults with major depressive disorder (MDD) show elevated levels of IL-6 and TNF-alpha. Studies of adolescents with MDD or anxiety disorders (AD) are few and present conflicting results. Methods: We studied plasma cytokines in a clinical sample of adolescent females with MDD and/or clinical AD (n = 60, mean age 16.8 years), compared to healthy controls (n = 44; mean age 16.5 years). Results: The clinical sample showed significantly higher values of IL-2 (Z = -4.09, p > 0.0001), IL1-beta (Z = -2.40, p<0.05) and IL-10 (Z = 2.38. p<0.05) as compared to controls. The subgroup of the clinical sample not treated with SSRIs had a significant difference of IL-6 (Z = -2.26, p<0.05) in addition to the difference of IL-2 and IL1-beta, but showed no difference of IL-10 as compared to the controls. SSRI treatment was related to IL-6, explaining 26% of the variance in the clinical sample after controlling for BMI and symptom severity. In the clinical sample, levels of IL-6 and IFN-gamma were positively correlated with self-assessed symptoms of anxiety and/or depression (corr.coeff 0.35 resp 0.40 at p<0.05). Limitations: The cross-sectional design does not allow for conclusions on causality. The sample sizes were relatively small and a large drop-out in the clinical sample may have influenced the representativity. Discussion: The study suggests that pro-inflammatory cytokines are part of the pathophysiology of emotional disorders in adolescent females and that SSRIs have anti-inflammatory properties. The findings prompt further studies on the specific mechanisms involved and may contribute to the development of more effective treatment and prevention. (C) 2011 Elsevier B.V. All rights reserved.