The Effects of Alpha-Theta EEG Biofeedback Training on Anxiety and Stress: Novel Use of Hair Cortisol Concentration as a Biomarker

Abstract

Electroencephalographic (EEG) biofeedback is a widely used nonpharmaceutical intervention for enhancing human functioning. This pilot study examined whether 24 sessions of alpha-theta (AT) training would reduce stress, as measured by hair cortisol concentration (HCC) and subjective anxiety scales, in 11 adults with generalized anxiety disorder (GAD). Pre- and postintervention measures included the State-Trait Anxiety Inventory (STAI), the Perceived Stress Scale (PSS), and HCC from hair samples. A novel 5-point Likert scale assessed five areas of functionality. Wilcoxon signed-rank tests revealed significant decreases in STAI and PSS scores (p < .01), with large effect sizes (d = 1.174; d = 1.655). Likert responses were positive, with most improvement in resilience and emotional status. Eight participants showed decreased postintervention HCC, though overall changes for N = 10 were not statistically significant (p > .01), as they included participants who did not respond to the training. The magnitude of HCC change indicated a moderate effect size (d = 0.62). In responders, HCC reduction was significant (p = .006) and linked to higher crossover percentages, suggesting deeper AT learning may lower cortisol. This is the first study to show the potential of AT training as a nonmedication approach to anxiety and stress reduction, with HCC being a novel objective biomarker.