Brain-derived neurotrophic factor (BDNF) is a protein that helps regulate brain and nervous tissue growth and plasticity, and low levels of it have been implicated in depression. For instance, the rapid effect of wake therapy (sleep deprivation) in depression seems to be correlated with BDNF levels. One study found that a failure of BDNF to rise with antidepressant drug treatment predicted treatment failure. The early non-increase of serum BDNF predicts failure of antidepressant treatment in patients with major depression: A pilot study
In the treatment of patients with major depressive disorder (MDD), early non-improvement of symptoms after initiation of antidepressant treatment is a highly sensitive and specific marker for final treatment failure. On the other hand, meta-analyses of clinical studies investigating serum BDNF (sBDNF) concentration before and after antidepressant treatment showed an increase of sBDNF during treatment, which was correlated with amelioration of depressive symptoms. No study has yet investigated the predictive value of early changes of sBDNF for final treatment outcome of the individual patient. The aim of this study was to investigate in patients with MDD, whether i) the non-increase of sBDNF in the early course of treatment is a specific and sensitive marker for final treatment failure, ii) whether the sensitivity and specificity of early non-improvement for treatment failure can be increased by combining it with the marker “early non-increase of sBDNF”. For this purpose, we performed a pilot study with 41 inpatients with MDD according to DSM-IV, who were treated in a naturalistic setting. Depression severity and sBDNF were measured in weekly intervals from baseline to week six with the 21-item Hamilton Depression Rating Scale (HAMD-21) and ELISA, respectively. The individual markers sBDNF non-increase and HAMD-21 non-improvement from baseline to day 7 or 14 predicted later non-response and non-remission with moderate to high specificity. The combined marker sBDNF non-increase plus HAMD-21 non-improvement at day 14 increased the specificity for non-response and non-remission to 100%. Our data provide the first evidence that the absence of an early increase of sBDNF in conjunction with early non-improvement might be a highly specific peripheral marker predictive for treatment failure in patients with MDD. If replicated, this combined marker could be considered useful for prospective confirmatory trials in patients with MDD.
Seems as if BDNF is closely and negatively correlated with depression.
To speculate a bit, exercise is known to be effective in treating depression, and exercise increases BDNF levels as well as increasing growth of neurons. This would also seem to put the kibosh on neurotransmitter theories of depression.