Transcutaneous vagal nerve stimulation for the treatment of trauma- and stressor-related disorders: systematic review of randomised controlled studies.

Background: Vagal nerve stimulation (VNS) has recently emerged as a prospective therapeutic approach for addressing trauma- and stressor-related disorders (TSRDs).

Aims: We assessed findings from randomised controlled trials for the safety and efficacy of VNS as a viable treatment for TSRDs.

Method: We systematically searched Medline, Embase, PsycINFO, CINAHL, Web of Science, Cochrane Central databases, trial registries, preprint servers and Google Scholar from inception to December 2023. Rayyan software was used for screening procedures. Two reviewers independently completed data extraction based on the inclusion criteria.

Results: We synthesised data by using a narrative approach. A total of 322 abstracts were identified and assessed, and seven studies were included in the review. Based on evidence synthesis, the present state of VNS as a treatment intervention for TSRDs, namely post-traumatic stress disorder (PTSD), is limited and does not meet clinical expectations. The overall certainty of evidence was very low. However, evidence shows that VNS may alter and reduce specific aspects associated with PTSD phenomenology, including the reduction of anger responses and the attenuation of hyperarousal during psychological interventions.

Conclusions: Although preliminary analyses provide evidence that transcutaneous VNS temporarily increases parasympathetic activity under specific conditions, these effects appear to be short-lasting, and the impact of repeated administration on long-term autonomic function remains unknown. Future randomised control trials should evaluate the therapeutic efficacy of VNS for treating TSRDs.