Introduction:
The underlying pathophysiology of unipolar and bipolar depression is receiving growing interest from researchers. One of the most prominent venues is the cytokine hypothesis. Because unipolar and bipolar depression are hard to differentiate from one other (especially in an early stage), there is a need for understanding the underlying etiology and pathophysiology. The present study aimed to define the difference between current depressive patients with and without manic symptoms at baseline and follow-up and healthy controls by measuring inflammatory markers.
Methods:
Baseline measurement of C-reactive protein (CRP), Interleukin-6 (IL-6) and Tumor Necrosis Factor alpha (TNF-α) were performed in a large group of currently depressed patients (N=957) assesd by Composite Interview Diagnostic Instrument CIDI and healthy controls (N=430). Then the presence of manic symptoms was assessed using Mood Disorder Questionnaire (MDQ) on baseline and 2 year follow-up. Based on the MDQ groups were formed and the mean inflammatory marker values were compared with eachother, before and after adjustment for possible confounding factors (sociodemographics, lifestyle and disease-related factors).
Results:
After adjustment for possible confounders, no significant difference was found between depressed patients with and without manic symptoms and controls in the cross-sectional analyses. However, the prospective analyses showed that high CRP levels in currently depressed men predict the development of manic symptoms in follow up (p<0.001).
Conclusion: These findings show that high levels of CRP in currently depressed men may predict the onset of manic symptoms at follow-up.
