SERPINE1 and major depressive disorder: Six studies20 , 21 , 23 - 26 that reported mean ± SD were included in the meta-analysis with a total of 507 MDD patients and 3,453 adjusted healthy controls, the overall SMD was 0.27 (95%CI 0.01-0.53); serum PAI-1 levels were 0.27 SDs higher in depression patients than controls.