BDNF and depressive disorder: However, a large body of studies showed that abnormal monoamine transmitters/receptor systems, altered stress hormone dynamics, deficient growth factors and neurotrophins, dysregulated pro-inflammatory cytokines, disturbed adult neurogenesis, altered synaptic connectivity, oxidative stress, abnormal miRNA expression, and abnormal delivery of gastrointestinal signaling peptides are associated with the pathogenesis of depression [4,5,6,7].