Background: Recent attention has been given to the role of biomarkers in psychiatric disorders. Bipolar Disorder (BD) has been associated with dysfunction of neuroplasticity and inflammation. However, the impact of these factors on disease progression remains unclear.
Objectives: To assess the role of brain-derived neurotrophic factor (BDNF) levels and cytokines as predictors of outcome in BD.
Methods: Serum levels of BDNF and the cytokines TNF-α, IL-6, and IL-10 were measured in 25 patients with BD at the time of recovery from their first manic episode. Patients were followed prospectively for one year, and the number of mood episodes and the amount of time spent with mood symptoms were assessed using standard clinical rating scales and NIMH Life Charts. We examined the relationship of the biomarkers with these clinical variables through a correlation matrix. Significant associations were entered as covariates in a regression model.
Results: IL-6 was positively correlated with number of days depressed during the one year follow-up (r=.528, p=.007). There was no significant correlation between BDNF, IL-10 or TNF-α and number of episodes or number of days with any mood symptoms. In a regression model controlling for age, IL-6 significantly predicted the number of days depressed.
Conclusions: The pro-inflammatory cytokine IL-6 is positively correlated with the number of days depressed during a one-year follow up after a first manic episode in patients with BD. To our knowledge this is the first report of a serum biomarker as a potential predictor of outcome in BD.