Stimulated brains and meditative minds: A systematic review on combining low intensity transcranial electrical stimulation and meditation in humans

Abstract

Background: Low intensity transcranial electrical stimulation (tES) and meditation are two promising, yet variable, non-pharmacological interventions. Growing research is investigating combined effects of both techniques on one's cognitive, emotional, and physical health.

Objective: This article reviews the current research that combines tES and meditation interventions in healthy and diseased participants. The review considers the intervention parameters and their effects in a well-organized manner.

Method: A systematic search for clinical and experimental published studies was conducted in the PubMed, Cochrane, and transcranial direct current stimulation (tDCS) databases using common keywords for tES and for meditation techniques well defined by previous studies. Unpublished ongoing studies were identified with the ClinicalTrials.gov and DRKS.de clinical trial websites.

Results: 20 published studies and 13 ongoing studies were included for qualitative analysis. 13 published articles studied patients with chronic pain, psychological disorders, cognitive impairment, and movement disorders. Anodal tDCS was the only tES technique while mindfulness meditation was the most common meditation type. Eight studies had a main group effect, with outcome improvement in the active combined intervention. However, most published studies showed improvements after at least one combined intervention with variable effects.

Conclusion: Pairing anodal tDCS with meditation shows promising improvements of the physical, mental, and emotional aspects of daily life. Further studies are required to confirm the relevance of this combination in the clinic.

Keywords: Brain stimulation; Meditation; Transcranial direct current stimulation (tDCS); Transcranial electrical stimulation (tES); Yoga.

Fig. 2

Characteristics of the published studies. A) Number of studies published according to year. B) Hierarchical representation the characteristics of the published studies. The order of significance from the inside-out is the condition of the participants, whether it is double-blinded, and the meditation technique. The outer most layer is the study itself. All studies included tDCS as the tES technique. MM = mindfulness meditation, MBCT = Mindfulness-Based Cognitive Therapy, MBRP = Mindfulness-Based Relapse Prevention, MBSAT = Mindfulness-Based Substance Abuse Treatment, MBSR = Mindfulness-Based Stress Reduction, TW-FM = Treadmill Walking with Focused Meditation. The * represents the studies that have a cross over design. The ** represents the studies where tES and meditation technique are not implemented concurrently.

Fig. 3

Hierarchical representation of the stimulation parameters that was used in tandem with a meditation technique for the selected studies. The order of significance from the inside-out is the intensity (mA), duration, and then number of sessions. The number of sessions only represent those that were active sessions together with the meditation technique. The outer most layer is the study itself. The * represents the study that had two different stimulation intensities.

Fig. 1

PRISMA flow diagram depicting identification, screening (databases and reports), and inclusion strategies for the selection of the published and ongoing studies. * Includes duplicate records that were returned for multiple keyword searches. ** Includes ongoing and published studies. The PRISMA diagram was modified from Page et al. (2021).