Mild Brain Stimulation Reduces Short-Term Anxiety in Older Adults

Stress can elicit various responses, including anxiety and perceived threat, alongside physiological changes like sweating and pupil dilation. The researchers noted that a treatment could alleviate the emotional sensation of anxiety without impacting how stressful a person judges an event.

The research focused on alpha brain rhythms, which are electrical patterns occurring approximately 10 times per second and are associated with attention and emotional regulation. Transcranial alternating current stimulation (tACS) applies a weak electrical current rhythmically through electrodes placed on the scalp.

Researchers targeted the alpha frequency to determine whether it could aid individuals in managing their emotional responses to stress, focusing on the frontoparietal control network, responsible for directing attention and emotional management.

Led by Rubén Romero-Marín from the Autonomous University of Barcelona, the study included 42 healthy adults with an average age of 59, comprising 16 women, sourced from the Barcelona Brain Health Initiative. Participants were split into two groups: one receiving active stimulation (22 individuals) and the other a sham procedure (20 individuals) that mimicked the sensations of stimulation without a sustained current. The active group underwent 20 minutes of stimulation at 10 Hz, targeting the left frontal and parietal scalp areas.

Following the intervention, participants undertook a stress task that involved watching two circles on a screen, receiving a mild electric shock to the hand, accompanied by an unpleasant sound and bright flash whenever the circles collided. Researchers assessed state anxiety, perceived stress, brain electrical activity, skin conductance, and pupil responses.

The most notable outcome was a decrease in state anxiety, defined as the immediate feeling of anxiety. Scores on a questionnaire ranged from 20 to 80, with the active-stimulation group showing a decrease of 3.16 points after treatment, while scores in the sham group increased by 1.17 points. Although the difference was statistically significant, it was marginal, leading researchers to describe the result as a “modest, selective reduction in stress-evoked state anxiety.”

However, perceived stress levels remained unchanged; participants continued to view the challenging task as equally demanding regardless of the stimulation. This suggests that the intervention likely influenced emotional reactivity, rather than altering situational evaluations.

Brain activity findings were mixed. While resting brain activity did not show consistent changes in alpha power post-stimulation, there was a tendency for increased alpha activity in the left frontal region during the stress task for those in the active-stimulation group, potentially indicating enhanced emotional regulation under pressure.

Physical measures of stress did not exhibit clear effects from the stimulation. Variations in skin conductance and pupil responses during the sessions occurred in both groups, possibly indicating adaptation to the task rather than the effects of the treatment.

Significant limitations are present in the study, including the small size of the participant group and the fact that it involved only healthy adults with generally low anxiety levels, raising questions about applicability to individuals with anxiety disorders. Furthermore, only one session of stimulation was tested, and the researchers did not explore other active frequencies to determine if the results were specific to alpha stimulation.

The study titled “Reducing state anxiety with alpha-frequency transcranial alternating current stimulation” included contributions from Simon Fankhauser, Javier Solana-Sánchez, Ruben Perellón-Alfonso, Josep Maria Tormos-Muñoz, Luiz Pessoa, David Bartrés-Faz, Davide Cappon, Álvaro Pascual-Leone, and Gabriele Cattaneo.