Interestingly, serum GDF11 levels were significantly decreased in the blood of MDD subjects (n = 57), compared to healthy age-matched controls (n = 51) (medianCONTROL = 22.69 pg ml−1, interquartile range (IQR): 9.63–76.40), medianMDD = 11.66 pg ml−1 (IQR, 3.89–42.10); Fig. 6b). The gene discussed is GDF11; the disease is major depressive disorder.