Moving beyond belief: A narrative review of potential biomarkers for transcutaneous vagus nerve stimulation.

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.

A pilot study of bright light therapy in schizophrenia.

Negative symptoms and episodes of major depressive disorder in patients with schizophrenia are common and there is an overlap in symptoms. Unfortunately, there is no effective primary treatment for negative symptoms yet. Depressive disorder in patients with schizophrenia is associated with a decreased quality of life and an increased risk of psychotic relapses. Previous research has shown that Bright Light Therapy (BLT) has a positive impact on negative symptoms of patients with schizophrenia. Our aim was to investigate the feasibility and the effect of Bright Light Therapy in a severely ill population of patients who were admitted to a closed ward. This pilot study was a single center, open label add-on trial with two control groups and included 20 patients. RESULTS: Neither negative nor positive symptoms were affected. However, there was a trend towards increase on the general psychopathology scale of the Positive And Negative Syndrome Scale in the BLT group. BLT did not change daily mood ratings. One participant from the BLT group was withdrawn from the study due to a manic state possibly triggered by BLT. Patients participating in our study did not benefit from BLT. It was an additional burden on the participants and worsened general psychopathology at a follow-up. Based on this study, we did not find any beneficial effect of BLT for patients with schizophrenia.