Evidence for Locus Coeruleus–Norepinephrine System Abnormality in Military Posttraumatic Stress Disorder Revealed by Neuromelanin-Sensitive Magnetic Resonance Imaging

Background: The complex neurobiology of posttraumatic stress disorder (PTSD) calls for the characterization of specific disruptions in brain functions that require targeted treatment. One such alteration could be an overactive locus coeruleus (LC)–norepinephrine system, which may be linked to hyperarousal symptoms, a characteristic and burdensome aspect of the disorder. Methods: Study participants were Canadian Armed Forces veterans with PTSD related to deployment to combat zones (n = 34) and age- and sex-matched healthy control participants (n = 32). Clinical measures included the Clinician-Administered PTSD Scale for DSM-5, and neuroimaging measures included a neuromelanin-sensitive magnetic resonance imaging scan to measure the LC signal. Robust linear regression analyses related the LC signal to clinical measures. Results: Compared with control participants, the LC signal was significantly elevated in the PTSD group (t₆₂ = 2.64, p = .010), and this group difference was most pronounced in the caudal LC (t₅₆ = 2.70, Cohen's d = 0.72). The caudal LC signal was also positively correlated with the severity of Clinician-Administered PTSD Scale for DSM-5 hyperarousal symptoms in the PTSD group (t₂₆ = 2.16, p = .040). Conclusions: These findings are consistent with a growing body of evidence indicative of elevated LC-norepinephrine system function in PTSD. Furthermore, they indicate the promise of neuromelanin-sensitive magnetic resonance imaging as a noninvasive method to probe the LC-norepinephrine system that has the potential to support subtyping and treatment of PTSD or other neuropsychiatric conditions.