INS and major depressive disorder: Several studies have applied proteomic approaches in MDD populations in the past few years5, 6, 7, 8, 9, 10 (2–7 years) most of them with a relatively small sample size (range N=12–49) and four studies with larger sample sizes11, 12, 13, 14, 15 (range N=102–1589), of which one was conducted by our group.11 Proteins differentially expressed in these studies were mostly involved in inflammation, insulin-related pathways and metalloproteinases.