Assessments of relationship between clinical responses and serum BDNF levels

To explore the clinical applicability of serum mature BDNF and proBDNF measurements as biomarkers in depression treatment, we specifically examined the relationship between the clinical responses to antidepressant treatments and serum BDNF levels in both antidepressant groups using the following two approaches. One approach involved examining whether the measured baseline serum levels of mature BDNF and proBDNF would be adequate predictors of clinical responses to antidepressant treatments during the acute phase (e.g., 6–8 weeks) of depression treatment. Specifically, we examined the baseline levels of serum mature BDNF and proBDNF between responders and non-responders who were assessed at week 6. The other strategy was to evaluate the long-term effectiveness of antidepressant treatments by examining the associated changes in serum levels of mature BDNF and proBDNF in responders who achieved clinical responses by the final assessment day, week 24. Moreover, we also examined the ratio of the levels of mature BDNF and proBDNF according to a previous study [17].