Credibility and expectancy of breathwork protocol
394 participants completed the CEQ-6 after practising their first session of breathwork. Independent t-tests revealed no significant differences on credibility scores (M ± SD) between the intervention (17.7 ± 4.67) and control (17.7 ± 4.79), (In the intervention and control, 187 and 189 participants answered the brief optional open-ended question regarding overall experience at post-intervention, respectively. Of these responses in the CB and placebo group, 143 (76%) and 141 (75%) comprised positive sentiment, 11 (6%) and 14 (7%) negative, along with 33 (18%) and 34 (18%) neutral, respectively. The breathwork practices across both groups were generally well-received, mostly pertaining to relaxation effects (even if short-term). On top of this, no participants guessed the main hypothesis question correctly at follow-up: 80 (42%) and 75 participants (39%) answered this optional question in the intervention and control group, respectively. None mentioned the use of breathing at 5–6 bcpm and/or CB (and any of its other names, i.e., ‘resonance breathing’) nor placebo. Thus, the lack of difference on the CEQs, similar overall positive sentiment between arms, paired with blinding to the main study hypothesis, tentatively suggests masking and concealment of the intervention was successful.