Effects of multisession prefrontal cortex tDCS or taVNS on stress, perceived stress and sleep quality: a double-blind, randomized controlled study

Abstract

Introduction: Chronic stress is a condition characterized by prolonged stimulation, leading to mental and physical weakness. It can have detrimental effects on individuals' mental health and cognitive function, potentially causing various health issues. This article explores the potential of non-invasive neuromodulation techniques, specifically transcranial direct current stimulation (tDCS) and transcutaneous auricular vagus nerve stimulation (taVNS), in managing chronic stress and improving sleep quality.

Methods: The study conducted a randomized, double-blinded, controlled trial with participants experiencing chronic stress. In total, 100 participants were randomly assigned to one of four conditions: the anodal tDCS group (n = 50), the sham tDCS group (n = 50), the taVNS group (n = 50), or the sham taVNS group (n = 50). Within each condition, participants received five sessions of either active treatment or sham treatment, with 20 min of tDCS over the dorsolateral prefrontal cortex (2 mA) for the tDCS groups, or taVNS on the left ear (20 Hz) for the taVNS groups. At baseline, post-intervention, and 4 weeks thereafter, we evaluated stress using the Lipp's Inventory of Stress Symptoms for Adults (LSSI), perceived stress through the Perceived Stress Scale (PSS-10), and sleep quality via the Pittsburgh Sleep Quality Index (PSQI).

Results: The tDCS and taVNS interventions resulted in reduced stress levels, improved sleep quality, and enhanced perception of stress.

Discussion: These findings suggest that tDCS and taVNS hold promise as effective treatments for chronic stress, offering a safe and accessible approach to improving individuals' wellbeing and overall quality of life.

Clinical trial registration: https://ensaiosclinicos.gov.br/rg/RBR-2ww2ts8, identifier UTN: U1111-1296-1810; Brazilian Registry of Clinical Trials (REBEC) RBR-2ww2ts8.

Keywords: chronic stress; neuromodulation; sleep quality; transcranial direct current stimulation; transcutaneous auricular vagus nerve stimulation.

FIGURE 1

The timeline of the data collection process over 28 days. On the initial day (T0), participants completed sociodemographic profiles and pre-tests for the LSSI, PSS-10, and PSQI. Over the subsequent 5 days, participants in the active anodal tDCS or taVNS groups received daily 20-min sessions of neuromodulation, while sham groups received sham treatment for the same duration. On the seventh day (T1) and 4 weeks post-intervention (follow-up, T2), all participants completed post-tests for the LSSI, PSS-10, and PSQI.

FIGURE 2

CONSORT diagram. Flowchart of participants disposition throughout the study.

FIGURE 3

Changes in stress levels and sleep quality following tDCS intervention. (A) Mean scores on the LSSI questionnaire at baseline (T0), immediately post-treatment (T1), and follow-up (T2) for the active anodal tDCS and sham tDCS groups. (B) Mean scores on the PSS-10 questionnaire at T0, T1, and T2 for both groups. (C) Mean total PSQI scores at T0, T1, and T2 for both groups. Error bars represent standard error of the mean (SEM). *p < 0.05 within groups and ^#p < 0.05 between groups.

FIGURE 4

Effects of taVNS intervention on stress levels and sleep quality. (A) Mean scores on the LSSI questionnaire at T0, T1, and T2 for the active taVNS and sham taVNS groups. (B) Mean scores on the PSS-10 questionnaire at T0, T1, and T2 for both groups. (C) Mean total PSQI scores at T0, T1, and T2 for both groups. Error bars represent standard error of the mean (SEM). *p < 0.05 within groups and ^#p < 0.05 between groups.