Compared with melancholic depression, persons with atypical depression had higher levels of leptin, angiotensin-converting enzyme (ACE), fatty-acid-binding protein–adipocyte (FABPa), complement C3, insulin and beta-2-microglobulin (B2M), while having lower levels of insulin-like growth factor-binding protein 1 (IGFBP1), IGFBP2 and mesothelin (MSLN). This evidence concerns the gene B2M and melancholia.