Table 2.
Association of intervention parameters with intervention stress/anxiety reduction effectiveness among 72 included interventions.
| Parameter | N | p-Value |
|---|---|---|
| Study design | ||
| Study design (RCT vs. other) | 72 | 0.77 |
| Control group (yes/no) | 72 | 0.19 |
| Primary vs. Secondary stress/anxiety outcome metric | 72 | 0.78 |
| # stress/anxiety outcome measurements (1, 2, 3+) | 72 | 0.43 |
| Breath practice and implementation | ||
| Population | 72 | 0.14 |
| Breath practice pace | 72 | 0.01 * |
| Breath pace other than fast-only | 70 | 0.10 |
| Human-guided training (yes/no) | 72 | <0.001 * |
| # human-guided sessions (0, 1, 2−3, 4+) |
71 | <0.001 * |
| Human-guided training included within device-guided interventions (yes/no) | 15 | 0.03 * |
| Single vs. Multiple sessions | 72 | <0.001 * |
| Long-term vs. No long-term practice | 72 | 0.005 * |
| Intervention duration (1, 2−5, 6−30, or 31+ days) |
71 | <0.001 * |
| Session duration: | ||
| <5, 5–10, 11–20, or >20 m | 61 | 0.03 * |
| <5 or ≥5 m | 61 | 0.005 * |
| Among sessions ≥5 m: 5–10, 11–20, or >20 m |
52 | 0.81 |
| Group vs. individual practice vs. both | 67 | 0.79 |
| At-home practice (yes/no) | 72 | 0.24 |
N reports the number of interventions in which parameter value was reported and thus the number of interventions included in the corresponding Fisher’s exact test. p-values based on Fisher’s exact tests on two-way frequency tables of effective versus ineffective interventions that either did or did not implement each parameter (Table S1 shows frequency counts; Supplemental File S2 shows statistical tests). p-value ≤ 0.05 signifies that intervention effectiveness was not associated with that parameter. Highlighted parameters identified as components for conceptual framework of factors associated with effectiveness in the 72 stress reduction breathing interventions among the 58 studies included in this review. Control categories defined as follows: yes, active and/or non-active control; or no, no control or another breath intervention only. Population categories defined as youth, healthy adults, high-anxiety populations, clinical populations (acute), clinical populations (chronic), and simulated stress populations. Breath practice pace defined as slow only, fast only, combined fast and slow with or without ANB/UNB, and ANB/UNB alone. Human-guided training defined as use of live or pre-recorded audio or video human instruction throughout at least the initial breath session. Multiple sessions defined as performing breathing practice more than once. Long-term practice defined as performing ≥6 sessions over ≥1 week. m, minutes; vs., versus; #, number. * Statistical significance at p < 0.05.