Table 1.

List of BFB studies of stress mitigation

First author	Training	Control	Assessment	Training sessions and duration	Sample size and characteristics (male/female; training/control)	Occupation	Age of subjects	Results
De Jonckheere et al. (2014)	RSA-BFB	No control	HR	1 session	19 (10 male)	ND	22–60	Cardiac coherence index scores were higher during breathing exercise than random ventilation. However, further validation is required to confirm system performance
Whited et al. (2014)	HRV-BFB	No intervention	PSS and BSI	4–8 sessions	27	Undergraduate and graduate students	22.54 ± 3.82	Treated subjects exhibited greater parasympathetic responses during stress in post-treatment session. However, no treatment effects were evident on self-reported measures, psychological symptoms, or affect
Kudo et al. (2014)	HRV-BFB	Control group	Edinburgh postnatal depression scale	Daily sessions for 4 weeks	55	Women in the early postpartum period	31.9 ± 6.6	Intervention group showed a significant increase in HRV and reduced vagal activity. Other effects included reduced anxiety and quality of sleep
Sarabia-Cobo (2015)	Coherent heart training		The Maslach burnout inventory and Zarit burden inventory	Weekly 1-h sessions for 3 weeks	74	Caregivers of patients with dementia	50.9	Heart coherence and positive psychology training had effective results over a long period
van der Zwan et al. (2015)	HRV-BFB	MM, PA	PSS	Daily sessions for 5 weeks	75 (20 male), PA: 23 (5 male), MM: 27 (7 male), BFB: 25 (8 male)		26.19 ± 6.53	HRV-BFB, MM and PA were equally effective in reducing stress and related symptoms
Ratanasiripong et al. (2015)	HRV-BFB	MM and control	PSS and state anxiety score	Sessions 3 times a day for 4 weeks	89 (all female), BFB: 29; MM: 20; control: 31	Nursing students	19.27 ± 0.56	BFB significantly reduced anxiety and maintained low stress levels. Mindfulness training decreased anxiety and lowered stress levels
Palekar et al. (2015)	GSR-BFB	Not included	PSS, pulse rate, respiratory rate, BR	10-min daily for 5 days, weekly sessions for 3 weeks	43	Physiotherapy students with PSS scores above 20	19.30 ± 2.98	Pulse rate, respiratory rate, BP and PSS values significantly decreased after 3-week training
Dillon et al. (2016)	SCR	No intervention	TSST, perceived stress, HR and mood assessment	30 min	50		26.7 ± 5.1	BFB group showed significant reduction in stress level and HR after training compared to control group
Munafò et al. (2016)	RSA BF	Daily questionnaire diary	Pre- and post-training assessment using self-report questionnaires and physiological measures (HR, BP and SCL)	5 weekly sessions, 45 min	31; 15 control	Managers from public and private companies	48.37 ± 8.71	RSA-BF increased vagal control, decreased sympathetic arousal and reduced emotional interference
Kraemer et al. (2016)	Mind–body skills training (meditation, BF, guided imagery, relaxation, breathing and autogenic training)	No intervention	Self-assessment questionnaires (distress tolerance scale)	11 weekly 2 h sessions	52 (24 males)	Medical students	23.45 ± 1.5	Mind–body group showed improved distress tolerance subscales as well as reported a better capability to bear affective distress
Dziembowska et al. (2016)	HRV BF	No intervention	Self-assessment questionnaires (STAI) and EEG	10 BF sessions within 3 weeks	41	Athletes	18.34 ± 1.36
Meier and Welch (2016)	Pace breathing (BFB), self-paced walk (exercise)	Quietly studying	State anxiety and affect measurements, HRV	2 crossover sessions	32, (21 females)	College students	21.7 ± 3.1	BFB minimized anxiety and momentarily improved calmness. Exercise momentarily raised energy

BFB biofeedback, BSI brief symptoms inventory, HRV heart rate variability, MM mindfulness meditation, ND not described, PA physical activity, PSS perceived stress scale, STAI state trait anxiety