MMP9 and post-traumatic stress disorder: Similarly, MMP-9 levels followed a gradient, with Past PTSD (≤5 y) showing the highest median (418.70 ng/mL, IQR: 341.08–558.19) versus Past PTSD (>5 y) (175.00 ng/mL, IQR: 66.64–306.66) and the controls (48.99 ng/mL, IQR: 39.77–58.23) overall, a trend maintained across age strata (e.g., 460.07 ng/mL, IQR: 341.08–558.19, in 36–50 years for Past PTSD ≤ 5 y).