Why random assignment changes what a trial can claim
In a randomized trial, participants are assigned to treatment or comparison groups by chance. That matters because health workers who volunteer for a stress program may already differ from those who do not: they may be more stressed, more motivated, or more open to mind-body approaches. Randomization spreads those differences across groups, so a later gap in stress scores is more plausibly attributable to the intervention itself. A non-randomized single-arm study, by contrast, follows one group over time and asks whether their stress scores fell. That design can show a program is feasible and that people report feeling better, but it cannot rule out that the same improvement would have happened without the program.
The randomized evidence in this set is consistent with real short-term benefit. A three-arm randomized controlled trial of mindfulness-based stress reduction in non-physician health workers found post-intervention reductions in psychological distress compared with both an active stress-management course and a wait-list group [3]. A randomized comparison of telemedicine versus in-person heart rate variability biofeedback found that both delivery modes significantly reduced depression, anxiety, and stress across a 10-day intervention, with anxiety dropping after each session [1]. These designs support the claim that the programs did something, not merely that participants improved.
What single-arm and non-randomized studies can still tell us
Non-randomized work is not useless. A single-arm study of a mindfulness program with direct biofeedback for health care professionals reported reductions in perceived stress and mood disturbances [4]. Because everyone received the intervention, the study cannot isolate the biofeedback component or compare it to an alternative, but it does show that the program could be delivered and that participants' self-reported stress moved in the expected direction. That is useful for generating hypotheses and for checking whether a protocol is practical in a real workplace.
The limitation is interpretive, not observational. When a single-arm study reports lower stress, the finding is compatible with a genuine effect, but also with regression to the mean (people often seek help when stress is at a peak and then drift back toward their usual level), seasonal change, or the simple experience of being monitored and supported. Randomized trials are the design that addresses those alternatives. So the honest reading is that non-randomized studies add plausibility and practical detail, while randomized studies carry the weight when the question is whether the intervention caused the change.
How much stress relief, and does it last?
Where randomized trials report effect sizes, the short-term numbers can be substantial. In a randomized trial of auriculotherapy for occupational stress among Family Health Strategy workers, the treatment group showed a 16.3% reduction in occupational stress after the third session and a 23.7% reduction after the sixth, with effect sizes described as large and very large [2]. That is a concrete signal that a brief, structured intervention can move stress scores meaningfully in the short run.
Durability is the weaker part of the picture. In the mindfulness trial, most of the benefit was not maintained at the four-month follow-up; only one subscale of psychological distress remained significantly improved compared with the active comparison course [3]. The biofeedback pilot measured outcomes at 10 and 40 days and reported decreases across the intervention, but its comparison was between delivery modes rather than between intervention and no intervention [1]. So the evidence supports short-term relief more firmly than lasting change, and that gap is a property of the follow-up periods actually studied, not a proven absence of long-term effect.
What these trials still cannot settle about biofeedback specifically
A key caution is that most of these studies test multi-component programs rather than biofeedback in isolation. The heart rate variability biofeedback trial compares telemedicine with in-person delivery, so its stress reductions speak to the program as a whole, not to biofeedback versus nothing [1]. The mindfulness trial compares mindfulness training with an active course and a wait-list, not with biofeedback [3]. The single-arm study bundles biofeedback into a broader mindfulness program [4]. A review of mindfulness-based stress reduction for health care professionals likewise addresses stress and well-being outcomes without isolating biofeedback as the active ingredient [5].
That means the quality contrast between randomized and non-randomized designs is real, but it does not by itself tell us how much of any improvement comes from biofeedback specifically. The randomized trials strengthen the claim that structured stress-reduction programs help health workers in the short term; they do not establish that biofeedback is the component doing the work. For a reader weighing these conclusions, the safest summary is that randomization mainly raises confidence that the programs helped, while the question of which ingredient mattered most remains open.
Sources used in this answer
Addressing Mental Health Symptoms Among COVID‐19 Healthcare Workers: A Heart Rate Variability Biofeedback Pilot Study
A randomized comparison trial found that telemedicine and in-person heart rate variability biofeedback both significantly reduced depression, anxiety, and stress in frontline health care workers, with no significant difference between delivery modes.
Effectiveness of auriculotherapy on stress reduction in health workers: a controlled randomized clinical trial
A controlled randomized clinical trial found that auriculotherapy reduced occupational stress in Family Health Strategy workers by 16.3% after three sessions and 23.7% after six, with large to very large effect sizes.
Effects of mindfulness-based stress reduction on psychological distress in health workers: A three-arm parallel randomized controlled trial.
A three-arm randomized controlled trial found that mindfulness-based stress reduction reduced short-term psychological distress in non-physician health workers compared with an active course and a wait-list, but most effects were not maintained at four-month follow-up.
Incorporating biofeedback into the mindfulness in motion intervention for health care professionals: impact on sleep and stress
A non-randomized single-arm study reported that incorporating biofeedback into a mindfulness program for health care professionals was associated with reductions in perceived stress and mood disturbances.
Cultivating mindfulness in health care professionals: A review of empirical studies of mindfulness-based stress reduction (MBSR)
A review of empirical studies of mindfulness-based stress reduction for health care professionals addressed stress reduction and well-being benefits but did not compare randomized with non-randomized biofeedback trials.