A slow diaphragmatic breathing intervention for anxiety: How do respiration rate and inhalation/exhalation ratio influence self-reported anxiety?

The primary aim was to investigate how respiration rate and inhalation/exhalation ratio influence self-reported state anxiety during a single slow diaphragmatic breathing exercise session. Eight hundred and twenty-eight participants completed the study at two separate geographical locations (Poland and Spain). Participants performed a 10-min online guided breathing exercise. Respiration rates were sampled from a continuous uniform distribution (ranging from 6 to 12 breaths/min). Similarly, inhalation/exhalation ratios were treated as continuous variables and sampled from a uniform distribution for each participant. An application programed for this experiment displayed visual and auditory cues adjusted for each participant. Before and after the breathing exercise, each participant filled in the Current Anxiety Level Measure questionnaire. Self-trait anxiety was measured with the Clinically Useful Anxiety Outcome Scale. A linear regression model showed that respiration rate, trait anxiety, pre-test anxiety, and nationality (Polish/Spanish) were positively related to post-test anxiety levels. Adding quadratic terms of respiration rate and inhalation/exhalation ratio did not improve model fit. Polish participants exhibited higher post-test anxiety levels compared with the Spanish subsample. Age was negatively associated with post-test anxiety. No significant relationships between inhalation/exhalation ratio and post-test anxiety level were found. Slower respiration rates during a single-session breathing exercise are linearly associated with lower post-test anxiety levels in a large and varied sample. This study is the largest to date and may offer further guidance for predicting expected effect sizes for the relationships between anxiety and respiratory dynamics.