The Cz electrode was chosen because Procyanidin-B1 previous studies have shown this to be a reliable site at which the amplitude is higher than at other electrode sites. The dipole source analysis for the calculation of LDAEP has been used in several studies, producing results similar to those obtained when using cortical activity. Moreover, many LDAEP studies involving MDD, bipolar disorder, and anxiety disorder patients along with healthy controls have been conducted based on cortical activity. Thus, the current study calculated the LDAEP from the cortical activity instead of using dipole source analysis. In addition, quality control was conducted periodically, such as checking the stimulus intensity and the impedance of the electrical cap. The Coptisine-chloride present study found no differences in the serum BDNF level between depressive patients stratified according to illness severity, history of suicide a empts, and LDAEP values. In addition, there was no correlation between the serum BDNF level and any of the measured variables, including the LDAEP and psychometric rating except total BIS score. However, reanalysis of the subgroup with moderate-to-severe illness severity revealed some positive findings after stratifying it according to BDNF and LDAEP values. It was hypothesized that biological changes associated with BDNF levels are larger in patients with a greater severity of depression based on meta-analyses that have shown significant differences between the effects of antidepressants and placebo on changes in HAMD or MADRS scores in such patients. Thus, the sample was reanalyzed whilst excluding patients with mild depression. Lee and colleagues found that plasma BDNF levels were significantly lower in suicidal MDD patients than in their nonsuicidal counterparts, and this finding was corroborated by Kim and colleagues. The finding of the present study of no difference in serum BDNF levels between two subgroups divided according to history of suicide a empts is not consistent with the previous results. These conflicting results may be a ributable to differences in the severity of depression between the subjects included in the studies, since those in the present study were all outpatients while those of Lee et al. and Kim et al. were not. Furthermore, BDNF levels were measured in different media between the studies. Moreover, the serum BDNF level has been found to be about 100-fold higher than the plasma BDNF level. This large difference originates from the clo ing process releasing circulating BDNF stored in platelets. The total BIS and BHS scores were higher in the high-LDAEP subgroup than in the low-LDAEP subgroup. This indicates that depressed patients with low serotonin activity are more vulnerable to aggressive or impulsive behaviors, including suicidality, than are those with high serotonin activity. These results are consistent with previous results. In the present study, the high-BDNF subgroup had a higher LDAEP �C as indicated by lower central serotonergic activity �C than the low-BDNF subgroup. In addition, serum BDNF levels were positively correlated with LDAEP. Conversely, Lang and colleagues reported that serum BDNF levels were negatively correlated with LDAEP. However, there is a growing body of evidence that refutes the current BDNF hypothesis.