BDNF and post-traumatic stress disorder: Biomarker–PSQI-A correlations also varied: the No PTSD group displayed specific significant associations (e.g., Caspase-1 with Trauma NM: ρ = 0.39, p = 0.038; BDNF with Trauma NM: ρ = 0.41, p = 0.029), the PTSD ≤ 5 y group showed fewer such links (e.g., Glutamine with Nervousness: ρ = 0.45, p = 0.009), and the PTSD > 5 y group had none.