Interleukin-6 as a predictor of symptom resolution in psychological distress: a cohort study

Background. Elevated levels of interleukin-6 (IL-6) have been associated with the development of common mental disorders, such as depression, but its role in symptom resolution is unclear. Method. We examined the association between IL-6 and symptom resolution in a non-clinical sample of participants with psychological distress. Results. Relative to high IL-6 levels, low levels at baseline were associated with symptom resolution at follow-up [age-and sex-adjusted risk ratio (RR) = 1.15, 95% confidence interval (CI) 1.06-1.25]. Further adjustment for covariates had little effect on the association. Symptomatic participants with repeated low IL-6 were more likely to be symptom-free at follow-up compared with those with repeated high IL-6 (RR = 1.21, 95% CI 1.03-1.41). Among the symptomatic participants with elevated IL-6 at baseline, IL-6 decreased along with symptom resolution. Conclusions. IL-6 is potentially related to the mechanisms underlying recovery from symptoms of mental ill health. Further studies are needed to examine these mechanisms and to confirm the findings in relation to clinical depression.