NEFL and concussion: Another study conducted by Guedes and colleagues investigating the correlation between PTSD symptom severity and the peripheral levels of extracellular vesicle proteins and miRNAs in chronic mTBI reported that extracellular vesicles’ NfL levels were significantly increased in patients with a history of mTBI and were corelated with more-severe PTSD symptoms as compared to healthy controls and, for mTBI patients, with less-severe PTSD symptoms [27].