Figure 2b.

Kaplan–Meier curves for posttraumatic stress disorder (PTSD) persistence according to deployment and age of PTSD onset

Cohort 1: deployment-unrelated trauma, age of onset: 18 to 30 (n = 117)

Cohort 2: deployment-unrelated trauma, age of onset: ≥31 (n = 57)

Cohort 3: deployment-related trauma, age of onset: 18 to 30 (n = 114)

Cohort 4: deployment-related trauma, age of onset: ≥31 (n = 69)

Testing homogeneity of survival curves over strata: χ² = 6.58, df = 3, P = 0.09 (unweighted results)