BDNF has been extensively investigated as a potential therapeutic tool for spinal cord injuries (Awad et al., 2015), neurodegenerative diseases (Sampaio et al., 2017) and stem cell therapy (Pramanik et al., 2017) with unclear results in human studies (Zoladz and Pilc, 2010; Palasz et al., 2020). This evidence concerns the gene BDNF and neurodegenerative disease.