If one considers this line of reasoning correct, then it is tempting to speculate that decreased levels of BDNF in BD may very well represent an epiphenomenon, without implying causality; in support of this is the fact that the polymorphisms of the BDNF gene are not associated with BD [101] or with hippocampal volumes in neuropsychiatric disorders [102]. This evidence concerns the gene BDNF and Behcet disease.