Potential peripheral biomarkers associated with the emergence and presence of posttraumatic stress disorder symptomatology: A systematic review

•PTSD is associated with altered biological processes.•Reliable and accurate biomarkers for PTSD symptomatology remain undefined.•Literature primarily pertains to neuroendocrine and immune marker candidates.•Future research should consider prospective design and extensive follow up.•Critically, future studies should measure subclinical symptoms, prior trauma, and sex.