Mean serum BDNF levels at follow-up in cases that had not been treated with any antidepressant but had fulfilled the diagnostic criteria of current episodes for each mood disorder were 7.3 (s.d.=3.7) ng ml−1 for MDD, 12.8 (5.9) for minDD and 6.8 (4.2) for minDE with MDE history (Figure 1). This evidence concerns the gene BDNF and major depressive disorder.