Monteleone et al. (2008) [64], Nuernberg et al. (2016) [65], Aas et al. (2018) [39], and Mansur et al. (2016) [66] showed a significant decrease in BDNF serum levels in BD patients compared to HC, while Dias et al. (2009) [67], Chou et al. (2012) [68], and Rosa et al. (2014) [69] did not find any significant difference between patients and healthy controls. This evidence concerns the gene BDNF and Behcet disease.