BDNF and depressive symptom measurement: In addition, deficiencies of brain-derived neurotrophic factor (BDNF) have a role in depression, anxiety and other neuropsychiatric illnesses.55, 56 Indeed, the acute behavioral effects of SSRIs and tricyclic antidepressants seem to require BDNF signaling,57 suggesting that BDNF holds great potential as a therapeutic agent.58 Cell therapies focused on correcting BDNF deficiencies in mice have had some success.