The relationship between CP and circulating BDNF levels has been investigated in approximately thirty human studies (Behnoush et al. 2023; Blandini et al. 2006; Dimmek et al. 2021; Holmuratova et al. 2023; Kosciuczuk et al. 2022; Mozafarihashjin et al. 2022; Wang and Li 2021; Yang et al. 2022), with most focusing on fibromyalgia (Behnoush et al. 2023). This evidence concerns the gene BDNF and fibromyalgia.