BDNF and major depressive disorder: In addition, because psychiatric diseases such as depression and anxiety are associated with increased suicidality in diabetics32–34, and a low sBDNF level and the BDNF Met/Met genotype are closely related to these psychiatric diseases44, diabetes may be a risk factor for SI only among subjects with a low sBDNF level or with the BDNF Met/Met genotype because of their high vulnerability to psychiatric diseases.