https://www.selleckchem.com/products/ttnpb-arotinoid-acid.html I read with interest the recent meta-analysis by Katsanos et al.(1) The authors are to be applauded for their efforts and careful analysis. In view of the potential significance of the findings, a trial sequential analysis (TSA) was performed to assess the conclusiveness of the presented evidence. This article is protected by copyright. All rights reserved.Transcutaneous vagus nerve stimulation (tVNS) is a non-invasive neurostimulation technique that is currently being tested as a potential treatment for a myriad of neurological and psychiatric disorders. However, the working mechanisms underlying tVNS are poorly understood and it remains unclear whether stimulation activates the vagus nerve for every participant. Finding a biological marker of tVNS is imperative, as it can help guide research on clinical applications and can inform researchers on optimal stimulation sites and parameters to further optimize treatment efficacy. In this narrative review, we discuss five potential biomarkers for tVNS and review currently available evidence for these markers for both invasive and tVNS. While some of these biomarkers hold promise from a theoretical perspective, none of the potential biomarkers provide clear and definitive indications that tVNS increases the vagal activity or augments activity in the locus coeruleus-noradrenaline network. We conclude the review by providing several recommendations for how to tackle the challenges and opportunities when researching potential biomarkers for the effects of tVNS. © 2020 Society for Psychophysiological Research.Clinicians tend to overestimate their ability to recognize feigning behavior in psychiatric patients, especially if it concerns patients who have been admitted for observation. Feigning can be either externally motivated (e.g., for financial compensation, known as malingering) or internally motivated (e.g., to assume the "sick role," known as factitious diso