Non-invasive vagus nerve stimulation normalizes food liking and improves liking ratings in depression

Vagus nerve stimulation has shown potential to treat major depressive disorder (MDD) and the vagus nerve plays a prominent role in the regulation of food reward and energy metabolism. However, previous studies using vagus nerve stimulation yielded conflicting results regarding changes in food reward in healthy participants and participants with MDD. We investigated the acute effects of right transcutaneous auricular vagus nerve stimulation (taVNS) on ratings of liking and wanting of food and non-food items in 62 participants, including 31 patients with MDD. To test for taVNS-induced changes and evaluate group differences and associations with symptoms, we performed linear mixed-effects analysis with group-wise post hoc comparisons. taVNS increased liking of food cues in patients with MDD (p = 0.020), but not in healthy participants (p = 0.92). Specifically, taVNS induced larger improvements in food liking ratings with increasing scores of anhedonia (p = 0.029). Notably, across all participants, taVNS effects were negatively correlated (p_boot = 0.002) with the individual hedonic response (i.e., average food liking) suggesting a normalization effect such that lower food liking gets boosted and higher liking attenuated following taVNS. Our results show that taVNS acutely ameliorates hedonic responses to food in MDD suggesting that it could provide a powerful adjuvant to rapidly improve food hedonics. Further investigation is needed to examine taVNS effects on anhedonia beyond food rewards.