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.