IGFBP1 and major depressive disorder: When looking at the 24 markers that were significantly different between atypical depression and controls, 9 (37.5%) did no longer reach significance at the P<0.05 level when comparing heterogeneous depression vs controls (that is, ACE, IGFBP2, IGFBP1, MSLN, SHBG, GSTa, CRP, CPep and APN).