Comparing the Effects of Square, 4-7-8, and 6 Breaths-per-Minute Breathing Conditions on Heart Rate Variability, CO 2 Levels, and Mood.
Level 3 - non-randomized controlled study
Within-subject repeated measures comparative trial in healthy volunteers; abstract does not specify randomized sequence allocation.
PubMed 39864026 · doi:10.1007/s10484-025-09688-z
What was done
Eighty-four college students (60% female) completed four breathing conditions: 1) square breathing, 2) 4-7-8 breathing, 3) 6 breaths per minute (bpm) with a 4:6 inhale-to-exhale ratio, and 4) 6 bpm with a 5:5 ratio. Heart rate variability (HRV) was measured at baseline and during each condition using a 3-lead electrocardiogram. End-tidal CO2 (PETCO2) was measured with a capnometer, and mood was assessed after each condition using the Scale of Positive and Negative Experience (SPANE). Blood pressure was also monitored. Repeated measures mixed effects models were used to analyze the outcomes.
What was found
Breathing at 6 bpm increased HRV measures more than square or 4-7-8 breathing with small to medium effects (no exact numerical values or effect size statistics are reported in the abstract). None of the breathing conditions resulted in meaningful changes in blood pressure or mood. Breathing at 6 bpm unexpectedly led to mild over-breathing.
Why it matters
While square and 4-7-8 breathing are widely recommended in psychotherapy, 6 bpm breathing appears more effective for acutely increasing HRV, though it carries a higher risk of hypocapnia/over-breathing.
Limits
The abstract provides no raw numbers, confidence intervals, or p-values for any outcome. The study was conducted on a non-clinical sample of college students during acute laboratory sessions, without long-term follow-up, and the abstract does not report whether the condition sequence was randomized or counterbalanced.
Cited by
- context The 4-7-8 breathing technique was developed by Dr. Andrew Weil for the military to lower heart rate in high-stress situations.