CASP9 and post-traumatic stress disorder: Clinically, elevated CASP-9 levels in PTSD patients, particularly in the acute phase (≤5 y), impair adaptive coping (Problem-Focused and Emotion-Focused) and overall coping capacity, reflecting heightened stress responses and potential exacerbation of psychiatric symptoms such as hyperarousal (DSM-5 Criterion E) and avoidance (Criterion C).