In a study involving 42 US military personnel who reported mTBI within 18 months, significantly elevated levels of exosomal tau and Aβ42 were observed in neuronal-derived exosomes from the peripheral blood, compared to healthy controls.116 However, while the association between post-traumatic stress disorder and exosomal tau levels showed a trend, it did not reach statistical significance.116 Further research into exosomal p-tau-181 in 195 veterans with repeated mTBI found a weak, significant correlation with the total PCL-M score (PTSD checklist military version). This evidence concerns the gene MAPT and post-traumatic stress disorder.