NOS1 and post-traumatic stress disorder: In Past PTSD > 5 y, the negative correlation between nNOS and Problem-Focused Coping (Rho = −0.3; Figure 5A) demonstrates that despite decreasing nNOS levels (5.42–66.2 ng/mL), active coping remains impaired, possibly reflecting learned helplessness or persistent negative alterations in cognition (Criterion D).