Mindfulness augmentation for anxiety through concurrent use of transcranial direct current stimulation: a randomized double-blind study

Abstract

Transcranial direct current stimulation (tDCS) have revealed the capability to augment various types of behavioural interventions. We aimed to augment the effects of mindfulness, suggested for reducing anxiety, with concurrent use of tDCS. We conducted a double-blind randomized study with 58 healthy individuals. We introduced treadmill walking for focused meditation and active or sham tDCS on the left dorsolateral prefrontal cortex for 20 min. We evaluated outcomes using State-Trait Anxiety Inventory-State Anxiety (STAI) before the intervention as well as immediately, 60 min, and 1 week after the intervention, and current density from electroencephalograms (EEG) before and after the intervention. The linear mixed-effect models demonstrated that STAI-state anxiety showed a significant interaction effect between 1 week after the intervention and tDCS groups. As for alpha-band EEG activity, the current density in the rostral anterior cingulate cortex (rACC) was significantly reduced in the active compared with the sham stimulation group, and a significant correlation was seen between changes in STAI-trait anxiety and the current density of the rACC in the active stimulation group. Our study provided that despite this being a one-shot and short intervention, the reduction in anxiety lasts for one week, and EEG could potentially help predict its anxiolytic effect.

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

“…The published studies included 664 participants, after correcting for secondary analyses publications using the same participants, comprising of 56.93% females and 43.07% males ( Table 1 ). Seven out of the 20 studies were conducted in healthy individuals ( Badran et al, 2017 ; Clarke et al, 2020 ; Danilewitz et al, 2021 ; Hunter et al, 2018 ; Nishida et al, 2021 ; Robinson et al, 2019 ; Sefat et al, 2022 ), while the remaining studies tested the combination of tDCS and meditation in patient groups diagnosed with conditions such as chronic pain ( Ahn et al, 2019; Pimenta et al, 2021 ; Pollonini et al, 2020 ; Ramasawmy et al, 2022 ), psychological disorders ( Alizadehgoradel et al, 2021 ; Brooks et al, 2021 ; Brown et al, 2020 ; Gibson et al, 2022 ; Hung, 2019 ; Monnart et al, 2019 ; Witkiewitz et al, 2019 ), mild cognitive impairment ( Liao et al, 2021 ), and movement disorders ( Park et al, 2021 ). All the ongoing studies test the combined intervention in diseased populations ( Table 2 ).…”

“…However, more research is necessary to confirm whether the combined techniques is sufficient for a non-invasive treatment. On the other hand, it is possible that Nishida et al (2021) had such distinct results since participants were encouraged to practice mindful walking at home for 1 week prior to the last measurements and Sefat et al (2022) had increased functional connectivity but not in power spectral density (EEG) possibly due to having a cross over design and including yoga as its meditation technique, which its effects have not been as thoroughly investigated in combination with tDCS.…”

“…They found that E-meditation with tDCS at both 1 mA and 2 mA showed relevant mathematical improvements in positive affect of the participants ( Badran et al, 2017 ). To further test the potential impact of E-meditation on facilitating mindfulness acquisition, Nishida et al (2021) investigated brain function using electroencephalography (EEG) and anxiety levels following an intervention of 1 mA anodal tDCS applied at the left dlPFC concurrently paired with TW-FM. Participants in the active group reported one week later significantly lower state anxiety and current density of the alpha band at the rostral anterior cingulate cortex (rACC) which was significantly correlated to the anxiety scores than the sham group (sham tDCS+TW-FM).…”

“…Participants in the active group reported one week later significantly lower state anxiety and current density of the alpha band at the rostral anterior cingulate cortex (rACC) which was significantly correlated to the anxiety scores than the sham group (sham tDCS+TW-FM). The authors suggest that the immediate reduction in rACC alpha activity might modulate the long-term activity of the amygdala, hence reducing anxiety level ( Nishida et al, 2021 ).…”

“…Two studies, Danilewitz et al (2021) and Clarke et al (2020) showed no significant results and even worsened symptoms, respectively. Approximately less than half of the studies (40%: Ahn et al, 2019 ; Alizadehgoradel et al, 2021 ; Hunter et al, 2018 ; Liao et al, 2021 ; Nishida et al, 2021 ; Pollonini et al, 2020 ; Ramasawmy et al, 2022 ; Sefat et al, 2022 ) showed significant main effects from the combination of a meditation technique with anodal active over sham tDCS stimulation, where all but Nishida et al (2021) and Sefat et al (2022) had more than one active session. Five showed significant improvements without having any main or group effects (25%: Hung, 2019 ; Monnart et al, 2019 ; Pimenta et al, 2021 ; Robinson et al, 2019 ; Witkiewitz et al, 2019 ).…”