BDNF and major depressive disorder: In contrast, the response to antidepressant treatment is accompanied by an increase in BDNF mRNA levels in the hippocampus and prefrontal cortex [28]; an increase in serum BDNF concentrations is observed in individuals with depression undergoing psychotherapy or pharmacotherapy [27,29], which also correlates with improved memory and learning and with a reduction in the symptoms of this disorder [30].