BDNF and Stroke: For instance, the stability in plasma BDNF levels observed in stroke patients [16] remain compatible with increased BDNF levels in the ischemic brain, and differences in serum BDNF levels that have been reported between patients without post-stroke depression (PSD) and PSD patients [18], [19] do not necessarily indicate that increased BDNF production in the brain of PSD patients is compromised.