A single session of mild, rhythm-based brain stimulation modestly reduced immediate anxiety after a stressful task in healthy middle-aged and older adults, according to a study published in the Journal of Affective Disorders. The researchers describe the effect as a “modest, selective reduction in stress-evoked state anxiety.”
Led by Rubén Romero-Marín of the Autonomous University of Barcelona, the team tested 42 healthy adults from the Barcelona Brain Health Initiative, with an average age of about 59 and 16 women. Participants were randomly assigned to receive either active stimulation (22 people) or a sham procedure (20 people) that mimicked the procedure without delivering a sustained current. The active condition involved 20 minutes of stimulation at 10 Hz via electrodes placed over left frontal and parietal areas of the scalp.
Before and after the intervention, participants undertook a stress task in which two circles moved on a screen. When the circles collided, they received a mild electric hand shock, accompanied by an unpleasant noise and a bright flash. The researchers assessed state anxiety, perceived stress, brain electrical activity, skin conductance and pupil responses.
The clearest finding concerned state anxiety, a measure of how anxious a person feels at a given moment. On a scale from 20 to 80, those in the active-stimulation group showed a fall of 3.16 points after treatment, while the sham group rose by 1.17 points. The difference between groups was statistically significant, though narrowly, leading the researchers to call the result a “modest, selective reduction in stress-evoked state anxiety.”
The intervention did not alter participants’ broader appraisal of stress. Perceived stress did not appear to be less demanding after active stimulation, suggesting the treatment impacted emotional reactivity rather than stress appraisal.
In brain measurements, resting alpha power did not show a reliable change after stimulation. However, during the stress task, activity over the left frontal region showed a trend toward a larger increase in alpha activity in the active-stimulation group, which the authors suggested could reflect stronger regulation of emotional information under pressure.
Physical stress markers were less conclusive. Skin conductance and pupil responses changed between the first and second sessions in both groups, which may reflect learning or task familiarisation rather than a specific effect of the stimulation.
The study carries several caveats. It involved only healthy adults with relatively low anxiety, so the findings may not extend to those with anxiety disorders. The sample was small, and technical problems reduced the number of participants available for physiological analyses. Only a single stimulation session was tested, and no other active frequency was evaluated, limiting conclusions about the specificity of the alpha-frequency approach.
The research, titled “Reducing state anxiety with alpha-frequency transcranial alternating current stimulation,” was authored by Rubén Romero-Marín, 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.
