Supplementary Material for: Effects of cranial electrotherapy stimulation in patients with post COVID-19 condition on anxiety symptoms - a randomised controlled trial

Introduction
People with post-COVID condition (PCC) suffer from a wide range of symptoms, including anxiety. Studies have already shown that cranial electrical stimulation (CES) has a positive effect on anxiety in anxious people. This randomised, controlled, double-blind, single-centre pilot study aimed to investigate the effects of CES as an adjunctive therapy during a rehabilitation on anxiety symptoms in people with PCC.
Methods
Adults with PCC were randomised to an intervention group with rehabilitation and (CES) (100μA) or a control group with rehabilitation and sham stimulation. CES was applied via electrodes to the earlobes for 60 minutes daily for 3 weeks. The Beck Anxiety Inventory (BAI) score was collected at baseline and at discharge.
Results
Forty people with PCC completed the trial. We found that both groups with (n=20) and without CES (n=20) improved significantly in terms of change in the BAI score (CESgroup: p=0.037; shamgroup : p=0.018), with no difference between groups (p=0.82). In a subgroup analysis of anxious patients only (BAI:≥16 pts, baseline score), both groups (CESanxious: n=10, shamanxious: n=10), significantly improved the BAI-score (CESanxious: p=0.008; shamanxious: p=0.002) with no difference between groups (p=0.69).
Conclusion
This study suggests that CES had no additional benefit on anxiety symptoms during rehabilitation in people with PCC.