“The endocannabinoid system is known to have positive effects on depression partly through its actions on neurotrophins, such as Brain-Derived Neurotrophic Factor (BDNF). As BDNF is also considered the major candidate molecule for exercise-induced brain plasticity, we hypothesized that the endocannabinoid system represents a crucial signaling system mediating the beneficial antidepressant effects of exercise…

These findings provide evidence in humans that acute exercise represents a physiological stressor able to increase peripheral levels of AEA and that BDNF might be a mechanism by which AEA influences the neuroplastic and antidepressant effects of exercise.”

http://www.ncbi.nlm.nih.gov/pubmed/22029953

“Neuroplasticity – exercise-induced response of peripheral brain-derived neurotrophic factor: a systematic review of experimental studies in human subjects. Exercise is known to induce a cascade of molecular and cellular processes that support brain plasticity. Brain-derived neurotrophic factor (BDNF) is an essential neurotrophin that is also intimately connected with central and peripheral molecular processes of energy metabolism and homeostasis, and could play a crucial role in these induced mechanisms… We can only speculate which central regions and peripheral sources in particular circulating BDNF originates from,…” http://www.ncbi.nlm.nih.gov/pubmed/20726622

“Preliminary evidence of cannabinoid effects on brain-derived neurotrophic factor (BDNF) levels in humans… cannabinoids modulate brain-derived neurotrophic factor (BDNF)… Delta(9)-THC increased serum BDNF levels…” http://www.ncbi.nlm.nih.gov/pubmed/18807247

“Antidepressant-like effects of Δ⁹-tetrahydrocannabinol…” http://www.ncbi.nlm.nih.gov/pubmed/22634064

“Antidepressant-like effects of cannabidiol… CBD treatment did not change hippocampal BDNF levels… CBD induces antidepressant-like effects…” http://www.ncbi.nlm.nih.gov/pubmed/20002102