2009; Ziegenhorn et al. 2007]. Furthermore, Kim and colleagues and Lee and Kim investigated BDNF levels in the plasma of depressive patients and also found unchanged levels [Kim et al. 2007; Lee and Kim, 2008]. We had difficulties in comparing our results with those of the other studies since subtypes of depression were not defined or evaluated as separate groups in almost all of the studies. Inhibitors,research,lifescience,medical We found

that patients with recurrent depressive episodes have lower BDNF serum levels compared with patients with a single episode and learn more healthy controls. This finding is in line with the study of Dell’Osso and colleagues who stated that patients who were suffering from a recurrent episode had significantly lower levels of plasma BDNF [Dell’Osso et al. 2010]. Kauer-Sant’Anna and colleagues have shown that bipolar patients later in the course of their illness have greater decrements in BDNF compared with those earlier in the illness, suggesting a possible cumulative deficit in BDNF after multiple episodes Inhibitors,research,lifescience,medical Inhibitors,research,lifescience,medical [Kauer-Sant’Anna et al. 2009]. Furthermore, there are several studies indicating that BDNF levels correlate negatively with increased severity of depression [Karege et al. 2002; Shimizu

et al. 2003; Gonul et al. 2005; Dell’Osso et al. 2010; Bus et al. 2011]. However, we also assessed the severity of depression with the use of HDRS and did not find any relation between the severity of depression and BDNF levels. This finding was in line with the study of Lee and colleagues Inhibitors,research,lifescience,medical [Lee et al. 2007]. The number of studies investigating the association

of VEGF with depression is limited. Kahl and colleagues found increased concentrations of VEGF in nonmedicated depressive patients with borderline personality disorder in comparison with healthy controls [Kahl et al. 2009]. Iga and colleagues had previously Inhibitors,research,lifescience,medical suggested that a higher expression of VEGF mRNA in the peripheral leucocytes might be associated with the depressive state [Iga et al. 2007]. Takebayashi and colleagues reported that plasma VEGF levels were increased significantly in MDD patients compared with matched controls [Takebayashi et STK38 al. 2010]. However, patients were taking psychotrophic agents in the last two studies. In parallel with our findings Dome and colleagues and Ventriglia and colleagues did not find any significant differences in serum VEGF levels between the MDD patients and healthy controls [Dome et al. 2008; Ventriglia et al. 2009]. In a recent animal study, Elfving and colleagues reported that VEGF levels were significantly decreased in the hippocampus and frontal cortex of a genetic depression rat model [Elfving et al. 2010]; however, no such difference was observed in serum levels of VEGF.