Recently, BDNF and pro-BDNF levels in CSF were shown to be associated with survival in ALS patients; in line with our discussion, C9-ALS patients showed significantly lower serum BDNF levels than non-carriers.79 Finally, monitoring of BDNF levels to assess both therapeutic efficacy and participant safety, particularly given its hormetic nature and the potential for excitotoxicity, will be important in trials investigating modulators of BDNF signalling, such as TrkB receptor agonists.80 Here, BDNF is linked to amyotrophic lateral sclerosis.