Rationale, design, and methods: A randomized placebo-controlled trial of an immunomodulatory probiotic intervention for Veterans with PTSD

•The prevalence of trauma-related disorders is increasing, and interventions are limited.•Inflammation and altered autonomic system activity may be treatment targets.•Immunoregulatory probiotics may decrease inflammation and associated symptoms.•This is a Phase IIa trial of LGG for United States military Veterans with PTSD.•We are using a longitudinal, double-blind, randomized placebo-controlled design.