Growing evidences suggest a role for BDNF in the pathophysiology of brain-associated illnesses such as OCD (Maina et al., 2010), attention deficit-hyperactivity disorder (Scassellati et al., 2014), eating disorders (Monteleone et al., 2006) substance abuse (Zanardini et al., 2011) as well as MD, BD and SCZ (Sen et al., 2008; Adachi et al., 2014; Polyakova et al., 2015). The gene discussed is BDNF; the disease is Behcet disease.